- Katashi: "You really think Yuki got in here and ate this stuff?"
- Dr. Deaton: "Actually, I think Yuki probably doesn't come anywhere near here. I doubt if you could even drag him in. Some part of him probably senses what happened here. To your father and the nogitsune possessing him. This particular lichen is called Letharia vulpina. Wolf lichen. They used it to poison wolves and foxes. They'd put out pieces of meat with crushed glass and bits of the lichen in it. The glass perforated the intestines of the animal so the vulpinic acid could reach the internal organs faster."
- — Dr. Alan Deaton to Katashi[src]
Deucalion and Talia are in a meeting with Deaton at the animal clinic. He says that their willingness to extend an olive branch to the Argents is admirable, but Talia thinks Gerard is unlikely to accept it. Deaton thinks that Talia means it's the matriarch of the Argents who they should be dealing with, but she clarifies that she just meant Gerard is a psychopath. Deucalion is surprised that they have so little faith in humanity. "You think that Gerard isn't worried about the deaths on his own side?" Deaton replies by telling them the story of The Scorpion and the Frog. The scorpion asked the frog to carry him across the river, and the frog asked, "How do I know you won't sting me?" The scorpion replied, "Why would I do that? Then we'd both drown." So the frog agreed. Halfway across the river, the scorpion stung the frog. The frog asked him why he did it since now they would both die, and the scorpion replied, "It's my nature." His point is that faith in humanity isn't the concern as much as Gerard's nature is. Deaton arranged a meeting between Gerard and Deucalion. After Deucalion is ambushed, Deaton unwraps the bandages from Deucalion's face. Deaton tells him that his eyes will heal physically but his sight will be gone. Duke roars and collapses against the table. He orders the others to leave him alone, and Talia and Deaton leave. 
A couple of years later, the Hale House is set on fire and most of the Hale family is killed.
Scott rushes to work and apologizes profusely to Dr. Alan Deaton. Deaton assures him that he doesn't think he's a slacker. When Scott turns around, he sees Sheriff Stilinski through the door. It turns out, however, that the Sheriff was bringing in a police dog to get its stitches out. He greets Scott and then asks Deaton if he can take a look at some crime scene photos for him since Sacramento can't determine what animal they're looking for. Deaton claims not to be an expert but looks at the photos of bite marks on Garrison Meyers. Sheriff Stilinski also mentions the wolf hairs on Laura Hale's body, and Scott can't help but comment. He repeats Stiles's information that there haven't been wolves in California in 60 years. Deaton explains that while that's true, wolves can wander in from far away, especially if they're motivated by a primal drive. Deaton points out that Garrison has claw marks on his face, but a wolf would have gone for the throat and spinal cord. The Sheriff asks if that means it's a mountain lion, but Deaton just can't say. A wolf could hobble its prey and then go for the throat. 
Dr. Alan Deaton calls Scott because he's an hour late for work. The Sheriff then comes in and shows Deaton some frames from a security camera in a parking lot near the video store. He lays down three photos, one of something coming through the window, one of something on all fours, and a final of a man. "I've never seen a mountain lion do that," the Sheriff says. Deaton tries to deflect him, telling him that he needs an expert opinion, and then goes to treat a sick dog. 
Derek goes to the Animal Clinic, and Deaton asks if he can help him. Derek asks him about a deer 3 months ago that had a spiral on its side. Deaton tells him that he was called to give an opinion on such a thing and reported that he'd never seen anything like it. Derek stalks forward asking if he heard the sound of his heart beat rising. Derek grabs Deaton, hauls him over the exam table, and then ties him to a chair. When he comes to, Deaton tells Derek where the keys to drug locker are. Derek replies that he just wants to know why he's lying. Derek lifts Deaton and the chair he's tied to off the ground and demands to know who he is and who he's protecting. Scott shows up then and yells at Derek. Derek drops Deaton and punches him, claiming that when he's unconscious he can't keep himself from healing. Scott tries to get between them, and Derek tells him that the spiral is their sign for a vendetta. "It means he won't stop killing until he's satisfied." Derek goes to hit Deaton again, but Scott wolfs out and grabs his arm to stop him. Derek stares, surprised, and backs off. "Hit him again, and you'll see me get angry," Scott says, shifting back. Derek paces while Scott cleans Deaton's wound. Scott tells Derek to meet him in an hour in the school parking lot. Derek pulls up with Deaton bound in the back seat. However, when they look again, he's gone. 
After the attack at the school, Scott notices Dr. Alan Deaton in the back of an ambulance. He asks how he got out. "Not easily." And then he offers Scott a raise. 
Dr. Alan Deaton finds Scott in the woods and brings him back to the clinic to remove the bullets. Deaton tells him that 90% of the time he's mostly treating cats and dogs. He gives Scott a small smile to show that he knows more than he's saying. 
Scott wakes up on Deaton's exam table and hops to his feet. Deaton pats him on the chest and suggests he sit down. Someone comes into the clinic, and Scott tries to warn Deaton that it's Peter, but Deaton goes out to tell Peter that they're closed. Peter tells him he's there to pick up. "I'm not sure I remember you dropping off," Deaton replies. They speak to each other as though they're really talking about a pet, but Deaton doesn't give any ground. Peter tries to walk into the back room, but the gate between him and Deaton is made of mountain ash, and he is unable to cross the barrier. He throws a chair in anger, but Deaton doesn't flinch. "Let me be as clear as possible. We. Are. Closed." Peter takes his leave, but he tells Scott that there are other, more vulnerable people who can help him get what he wants. 
Scott drops a container at work and Deaton asks him if he’s got a lot on his mind. Scott says that everything is slipping through his fingers. Deaton tells him that it’s all about perspective and Scott asks if they are going to talk about “the thing they need to talk about,” referring to the current werewolf situation, but Deaton just offers him a raise, which they agree on. Later, Deaton arrives at the vet’s office with the alarm going off. Chris Argent has put a mauled body on the table and wants info on what killed the man. Scott goes to see Deaton about why the cut in his torso isn’t healing. Deaton tells him that wounds from an Alpha don’t heal as quickly. 
Deaton helps Scott clean out the wounds he got from the fight with Derek. There’s a dead man lying on the table with claw wounds raked down his body. Deaton tells Scott about a book sounding like a supernatural encyclopedia before Chris Argent, Gerard Argent, and another hunter walk into the vet’s office. Scott is hidden away in a closet as Deaton explains his theory about how the man was killed. Some monster paralyzed the man with venom to the neck before killing him with his claws. Deaton says he has no clue what killed him, but gives some characteristics, stating that the hunters should "be afraid, very afraid." 
Scott lets Derek and Isaac into the Animal Clinic. Scott asks what Isaac is doing there. "I don't trust him." "Yeah, well, he doesn't trust you either," Isaac replies. Derek says, "Derek really doesn't care!" Derek asks if Dr. Deaton is going to help, and Deaton replies that that depends on whether they're going kill Jackson or save him. Scott answers "Save him" and Derek answers "Kill him." Scott insists on saving him, and Derek relents. Deaton brings them into the back room and sets out a tray of bottles. Isaac goes to pick one up, but Derek grabs his wrist to stop him and tells him to watch what he touches. As Deaton checks through the bottles, Isaac leans on the table and asks him if he's some kind of witch. "No, I'm a veterinarian." Deaton tells them he doesn't have anything that would be an effective defense against a paralytic toxins. Derek tells him that they're open to suggestions, and Isaac asks about an effective offense. Derek tells him that he slashed its throat pretty deeply and Chris emptied a clip into it and it just got up again both times. Deaton asks if it's shown any weaknesses, and Derek tells him that it wouldn't go near water. Deaton asks if that's true of Jackson, and Scott tells him that Jackson is captain of the swim team. Deaton says that they're trying to catch two people: a puppet and a puppeteer. He holds a medallion up and then puts it on the table. They are also aware that the kanima killed Sean but the puppeteer killed Jessica. Deaton asks why the human had to kill the wife. Scott suggests that Jackson couldn't do it because his mom was killed while pregnant too, and was possibly murdered. Isaac suggests that it could be part of the rules. The kanima kills murderers. If it killed Jessica, then the baby would die too. Scott asks if that means Mr. Lahey was a murderer. Isaac woudln't be surprised if that were the case. Deaton then suggests that the kanima's fear of water isn't from Jackson but from the master. "What if something that affects the kanima also affects its master?" He takes out a jar of mountain ash and pours a circle around the medallion. 
Deaton helps Derek by cleaning his wound after he witnessed his uncle, Peter resurrect. 
Derek blinks awake. Dr. Deaton is kneeling over him. Derek asks what the sound was, and Deaton holds up a dog whistle, grinning. Derek smirks and tries to stand, but he stumbles. Deaton catches him and tells him that he's going to be weak for a few hours. Derek flashes back to Peter coming back to life and realizes it wasn't a dream. Deaton tells him that he's still an alpha, "but, as usual, not a particularly competent one." Derek lets the insult go and asks where Peter is. Deaton doesn't know. Derek demands to know why Deaton is helping him. "Helping your family actually used to be a pretty important part of my life. Helping you was a promise I made to your mother." Derek backs off and says that Laura told him there was a sort of advisor to their family. Deaton says that Peter's resurrection comes with a price. He will be physically weak, so he will rely on his intelligence and cunning. "He's going to come at you, Derek. He'll try to twist his way inside your head, preying on your insecurities. He'll tell you he's the only way you can stop Gerard. Do not trust him." Derek replies that he doesn't trust anyone. Deaton replies that if he did he might be the alpha he likes to think he is. "Unfortunately, the one person you should trust doesn't trust you at all." "Scott." Deaton tells him to find Scott as fast as he can because Gerard always has a plan and it's so far going exactly how he wants. Derek spends most of the conversation looking worried, even while Deaton is insulting him. 
Scott's working at the clinic. When someone comes through the front door, Dr. Deaton asks him to go see who it is, but before Scott can really move, the animals start going a little crazy. Deaton and Scott find Isaac standing in the front room, and Deaton invites him in. Isaac watches as they treat an injured dog. He asks why the dog smells the way it does. Deaton smirks. Scott said something similar to him awhile ago. All of a sudden he could tell which animals were getting better and which weren't. Isaac looks like he's about to cry when he says that the dog isn't getting better. "Is it cancer?" "Osteosarcoma. It has a very distinct scent, doesn't it?" Scott nods in agreement. Deaton invites Isaac to come closer. He says that Isaac knows what his abilities can do for himself, but he'd like him to learn what they can do for others. He asks Isaac for his hand, and then places it on the dog. Without really meaning to, Isaac starts drawing the pain into himself. He pulls back his sleeve to watch the black threads move up his skin. "What did I do?" Isaac asks. Scott tells him that he took some of his pain away. Deaton explains that it was only a little bit, but sometimes even a little can make a big difference. Isaac starts to cry, and Scott tells him that he cried the first time he did it too. 
After Gerard had escaped. Deaton examines the black ooze droplets Gerard left outside the warehouse. Ms. Marin Morrell asks him if he's planning on getting his hands dirty. He replies that he does what he has to. "Good, I never liked you being retired anyway." 
While talking with the Sheriff at the animal clinic, Deaton reveals that strange things are happing with the animals at the clinic as well, and that the animals are doing these things to themselves. 
Scott, Derek, Stiles, and Isaac go to the Clinic, where they’ve decided to put Isaac in ice water until his heartbeat slows enough for Deaton to have access to his subconscious and find his memories. This happens to be slow enough for Isaac to be nearly dead. Derek tells Isaac that he doesn’t have to do it if it’s just too risky, and Scott agrees with the sentiment, but Isaac decides that it’s what he wants to do. Scott and Derek submerge him in the water, and he shifts trying to surface. Between Scott, Stiles, and Derek they manage to keep him down until he stops struggling before allowing him to float back up. Deaton tells the others that only he can talk or Isaac will get confused. He asks Isaac to remember, and Isaac begins to get upset saying he doesn’t want to and the lights flicker before Deaton gets him under control again. Isaac says he found Erica and Boyd in a stone building, maybe marble, and it’s dusty and empty. Deaton manages to get him calm again before proceeding. Derek comments that if they are locked in together without restraints they’ll probably end up tearing each other apart. Isaac suddenly becomes distressed again, repeating over and over that "they’re here" and Derek tries to ask him where is he. Isaac is beginning to panic more, and Deaton and Scott want to back off, put Derek forges on, knowing that he must have seen something particularly important to be reacting this badly. Isaac spews out several rapid sentences before yelling that it’s a bank vault before coming to. They others help him out of the water, and he reveals that it’s Beacon Hills First National and the other betas are locked in the vault. When all he gets are hesitant looks from the others and asks why, Stiles reveals that the last thing he said before the bank was that he was in a room where he saw Erica’s body. 
At the vet’s office, Deaton gives a dog a shot as Scott helps the dog get ready. The next day, Stiles visits the animal clinic during his free period thinking Deaton could have information about the murders. Stiles is explaining what he’s found in regards to the druids and human sacrifices. Stiles realizes that Deaton is aware of everything he’s saying already, and Deaton admits that he’s been denying what’s going on because he’s spent a good ten years trying to avoid this. Apparently the murders are somebody copying an old druid ritual. Stiles's phone rings, and it’s Lydia telling him about how the band teacher has been taken. Stiles and Deaton go to the school to check out what Lydia found, and Stiles thinks that the next group is soldiers because Kyle was in ROTC and the band teacher was a former military officer. Stiles goes to call Boyd when Lydia remembers that Mr. Harris was also former military. The same chanting heard on the phone is heard in Harris’s classroom. Deaton, Lydia, and Stiles enter Harris’s classroom. He’s gone, but all of his stuff is still in the room. Tests graded as “R” and “H” are found, and Deaton puts them together to spell “darach”, the name for a druid who’s turned to the dark side. 
Scott and Deaton are at the animal clinic, where Scott is afraid that Derek is going to get his entire pack killed and wonders if he should try to stop them. Deaton tells him that he shouldn’t stop them, but lead them. Later, the doorbell rings and Morell enters with Aiden and Kali, carrying a mostly dead Ennis. Deaton doesn’t want to help them, and the pack can’t force its way in because the the clinic is made of mountain ash. Morell reasons that if Ennis dies the alpha pack will be out for blood and end up hurting the pack, and Deaton opens the gate. Deaton begins to work on Ennis. Deucalion arrives and talks with Deaton before crushing Ennis’s skull with one hand. Deaton is more than a little disturbed. Deaton warns Morrell about what she’s gotten herself into. 
Deaton calls Scott and tells him that he is the third sacrifice. Moths surround the animal clinic. He is moved to the bank vault where he is suspended from the sealing. Scott arrives at where Deaton is suspended by his arms. He hangs limply. Scott rushes forward but is shoved backward with a flash of light. He realizes that Deaton is surrounded by a circle of mountain ash. Scott tries again to penetrate the force field, pushing against it with all his might and filling the room with a blue glow. His eyes shine yellow then red as he pushes harder and harder, but the barrier will not bend, and Scott is thrown back to the floor. He looks on helplessly as Deaton hangs there. Sheriff Stilinski is suddenly in the doorway of the vault, gun in hand. He fires at the rope, and Deaton drops to the ground. The Sheriff explains to Scott and Deaton that he figured out where Deaton was because one of the Celtic symbols on one of the vials at the vet clinic reminded him of the bank’s logo. Deaton tells Scott about his eyes changing colors. He says Scott is a “True Alpha” one who rises on strength of character and sheer force of will as opposed to those who take the status from another alpha. Deaton says it's rare, happening only once in a hundred years but that he believed Scott had this potential in him since he was first bitten. 
Stiles won't talk. Agent McCall doesn't want Stiles going home alone and asks if he has anyone he can go home with. "He's with me," someone says from the doorway. It's Dr. Deaton. Everyone is gathered in the Animal Clinic. They figure the nemeton has to be on a telluric current, or maybe even at the point where two cross. Stiles explains that he only knows that it's where Derek took Paige to die. Allison adds that her father and Gerard were there once, but it was years ago and Gerard couldn't remember where it was. Deaton tells them that there might be a way to find it, but it's dangerous and they're going to need Scott. Deaton suggests that they focus on one thing at a time. The plan is that Scott, Stiles, and Allison will be surrogate sacrifices for their parents. "We die for them?" Scott asks. "But he can bring us back," Stiles adds, and then looks at Deaton to make sure. "You can bring us back, right?" Deaton reminds him that he said this was going to be dangerous. If everything goes right, they'll be dead for a few seconds. "You'll be giving power back to the nemeton, a place that hasn't had power for a long time. This kind of power is like a magnet. It attracts the supernatural, the kind of things that a family like the Argents can fill the pages of a bestiary with." Stiles thinks that that doesn't sound any worse than what they've already seen. "You'd be surprised at what you have yet to see," Deaton says. Deaton also explains that they will feel effects themselves. "It'll be a kind of a darkness around your heart, and permanent, like a scar." Deaton prepares three ice baths. There are herbs in the baths as well. Deaton asks them all what they brought. Stiles holds up his father's badge. Jennifer crushed it, but he hammered it out a bit. He apologizes for it not looking too great. "It doesn't need to look good if it has meaning," Deaton tells him. Deaton explains that they will each get in a tub and be held down until they're dead. But the person holding them under needs to be a tether who can pull them back, someone with a strong connection to them. Lydia looks at Allison and takes a step toward her, but Deaton tells her to go with Stiles instead. 
Allison gasps awake from the ice bath in the Animal Clinic. Scott and Stiles gasp awake as well and climb out of the tubs. Lydia, Isaac, and Deaton are waiting around. "I saw it. I saw where it is!" Scott tells them. Stiles adds that they passed it the night they were looking for the body and the tree is big. Cut down, but very big. Allison says that she was there too and they almost hit someone with their car. Scott realizes that she almost hit him. The three of them stop talking when they see that Deaton, Lydia, and Isaac are staring at them. "You guys were out a long time," Isaac says. "How long is a long time?" "16 hours," Deaton tells him. The full moon rises in less than four hours. Stiles argues with Scott about him going back to the alpha pack. Scott tells him that he made a deal with Deucalion. "Does anyone else think that sounds a lot like a deal with the devil?" Stiles says. Isaac asks why Scott wants to go back with them, and Scott says that he doesn't think they can beat Jennifer without them. Allison appeals to Deaton to change Scott's mind, but Deaton agrees with his plan. "So we're gonna trust him? The guy that calls himself Death, the Destroyer of Worlds, we're gonna trust that guy?" Isaac asks. Deaton says they should use Deucalion to their advantage and use him as bait. The Animal Clinic door opens, and everyone looks concerned. Deaton goes out and finds Ethan in the lobby. "I'm looking for Lydia." He says that he needs her help. Stiles comes into the doorway. "With what?" "Stopping my brother and Kali from killing Derek." Later, Cora and Lydia bring the twins to the Animal Clinic. They put each one on a table, and Lydia takes Aiden's hand. Cora asks Deaton if he can save them, but he has they have to start healing on their own. Deaton gives Ethan and Aiden oxygen and some shots. After a while, they heal but loose their alpha status. Deaton questions Scott on what just happened. 
Stiles and Scott go to visit Deaton. He tells Stiles that his subconscious is trying to communicate with him. "Well how do I tell my subconscious to use a language I actually know?" Stiles asks. Deaton has him repeat the signs and translates, "When is a door not a door?" "When the door is ajar," Scott supplies. Stiles in incensed that his subconscious is telling him riddles. Deaton says it's not necessarily a riddle. When the three of them sacrificed themselves, they opened a door in their minds that is still ajar. Scott asks what they do about it, and Deaton tells him that's difficult to answer. Stiles says that Deaton's face has the "we know exactly what's wrong with you and no idea how to fix it" look. Deaton tells them that they each need to close the door in their minds. 
Deaton is called for his assistance. The door panels draw back, revealing Dr. Deaton, flanked by more yakuza men. Deaton addresses the man in Japanese and apologizes. The boss tells him to apologize if he can't do anything. "Have you worked with wolves before?" the boss asks. Deaton smirks and replies, "Here and there." The wolf's name is Yuki. Deaton examines Yuki's teeth and then asks if he's been around any unusual plants, something that looks like moss. It would be bright green, almost neon. The yakuza all give each other shifty looks. Deaton tells them that he needs to know if Yuki has eaten any, and the boss is distressed. He wants Deaton to just treat him if he knows about the lichen, but Deaton insists that he needs to know the species of lichen first. The boss relents. He orders one of his men to take Deaton into the garden, but the man refuses. All of his men refuse to go into the garden. "Superstitious idiots," the boss says, and leads Deaton out. The head into the same garden where Chris Argent's first deal with the yakuza and first encounter with a nogitsune went down. The boss looks nervous and motions toward a fountain in the middle of the garden that's covered in lichen. This fountain is where the nogitsune bled as the Oni stabbed him. Deaton opens his bag and hands the boss a glass bottle. He gets down and starts to cut free a sample, while the boss asks him if he really thinks Yuki got into the garden and ate lichen. "Actually, I think Yuki probably doesn't come anywhere near here. I doubt if you could even drag him in." Deaton inspects the lichen and says that some part of the wolf probably senses what happened in the garden. "...to your father and the nogitsune possessing him," Deaton says. The yakuza boss points his gun at the back of Deaton's head. Deaton continues, unruffled. "This particular lichen is called letharia vulpina, wolf lichen. They used it to poison wolves and foxes. They'd put out pieces of meat with crushed glass and bits of lichen in it." The glass would perforate the intestines and allow the poison from the lichen to get in. The boss demands to know what Deaton did to his wolf. "Well, I didn't poison him with lichen, but I did give him a powerful paralytic agent." He used kanima venom, which he also put on the glass he handed to the boss. The boss loses his grip on his gun and collapses. Deaton takes his jar back and brandishes the lichen. "Born out of the blood of a nogitsune, this lichen is quite special. More powerful than you know." The boss asks what he's going to use it for, and Deaton replies that he's going to poison the nogitsune inside a teenager. Later, Deaton injects Stiles with letharia vulpina. Stiles collapses. Deaton pulls the sword out of Scott in one swift move. Scott asks if Stiles will be okay now. "The fox is poisoned, but it's not dead. Not yet." 
"Did you have any trouble with Ikeda?" Chris asks Deaton from a phone in the sheriff station. Deaton reports that everything went fine and the white wolf was exactly where Chris said it would be. He explains that their first problem is that the lichen isn't a cure and it will wear off in a matter of days. However, while it's working, the Oni won't go after Stiles. Deaton says that Eichen House has an unusual history that makes it dangerous for the Oni. The second problem is that the yakuza boss Chris saw die never found the scroll. "What scroll?" Scott asks. The shugendo were the ascetics mystics of Japan. The scroll describes how to exorcise a nogitsune. Deaton did find out that Kincaid was the last man who purchased it. Allison recognizes that as the name of Katashi's bodyguard. "Stilinski already told me that nothing like it was found among his things. And a paranoid like Katashi would keep it close, probably on him at all times," Chris says. Allison gets an idea and asks what a Shugendo scroll would look like. Deaton hands her a scroll, and she asks if they come in different sizes. "Any size," Deaton says. Allison knows where they should look. After they retrieve the scroll, Deaton reads it. He claims his Japanese isn't very good but that it says "One method of expelling a nogitsune is to change the body of the host." Deaton asks how they change Stiles's body, but Scott already knows the answer to that: make him a Werewolf. 
Scott and Aiden carry the nogitsune to the couch in Scott's living room. Melissa claims that this is crazy and that he should be in the hospital. "Mom, you remember what happened last time he went to the hospital?" Deaton examines the wound in the nogitsune's stomach and declares that he isn't bleeding. "I think he might even be healing." "You mean healing like we heal?" Aiden asks. Scott thinks that might be good. Deaton agrees that it's good for the nogitsune but probably not so good for them. Aiden asks why they aren't tying the nogitsune down with really big chains if they aren't going to kill him. Deaton says he has something more effective and puts a dropper full of kanima venom in the nogitsune's mouth. The nogitsune immediately awakens and grabs Aiden by the throat. Scott manages to break the grip, and then the venom does its work. "Kanima venom. Nice touch," it says to Deaton. Melissa asks if Deaton has anything that can shut the nogitsune up. Deaton tapes his mouth shut, and the nogitsune roars and laughs. Scott asks Deaton how much longer he thinks the venom will keep the nogitsune down. Deaton doesn't know, but he does know they're going to need a better place to keep him than Scott's house if they don't figure out something quickly. "He might be paralyzed, but it still feels like he's got us right in the palm of his hand." Lydia, Deaton, and Scott discuss giving the nogitsune the Bite. Deaton tells them that they may be looking for a cure in something that may be nothing more than proverb or a metaphor. Scott is concerned about giving Stiles the Bite at all, because he's never asked to be a Werewolf. Lydia argues that it could save his life, but Deaton points out that it could also kill him. Scott's never Bitten anyone before, so he's not sure what he should do or how to do it right. Deaton urges them to make a decision before the venom wears off. Scott wants to try calling Derek again, but Lydia suggests calling someone else. Peter links Scott and Lydia to the nogitsune. Lydia starts bleed from her nose. Melissa freaks out, but Deaton keeps her from getting any closer. Seemingly at the sound of her voice, the nogitsune spasms to life. He rips the tape off his mouth and starts pulling bandages out of his throat. He vomits up a whole pile of bandages and gasps for breath. A wrapped hand starts emerging from the pile, and something that looks like the nogitsune crawls from the floor. Peter and Scott tackle it and hold it down on the couch, with effort. It keeps scrabbling at the bandages on its face, though, and Scott tells Peter to wait. He pulls the bandages off, revealing a teary-eyed Stiles. "Scott?" Stiles looks around at all of them. Deaton then points out that the other Stiles, the nogitsune, and Lydia are gone and the back door is open. Scott races out the door calling Lydia's name. 
Deaton is at the school. "Hold still," Deaton says, as he shoves his hand down Ethan's throat to extract the nogitsune fly. He drops the fly down the drain, then grabs Isaac and hauls him under the shower next. He orders Isaac not to fight it as he shoves his hand into his mouth. Isaac gags and scrabbles at Deaton's arms until the fly is extracted. Isaac stumbles away and clutches at his throat. Allison asks if the Werewolf are okay now. Deaton thinks so, but the bigger worry is that all this was just a distraction for what was happening to Stiles. Kira and Allison ask how there could be two Stileses and how one could just kidnap Lydia. Aiden is upset that no one actually noticed the nogitsune kidnapping her right out of the house. "Most of us were concentrated on the bizarre sight of a creature materializing from out of the floor," Deaton snarks at him. Kira asks how they're so sure which Stiles is which, and Deaton admits that they're trying to figure that out now. 
Scott and Lydia meet up with Deaton at the Animal Clinic. They tell him about the nemeton keeping the nogitsune trapped. "The problem is this isn't even a person you're fighting. It just looks like one." Lydia points out that if someone caught it once, they can do it again. Deaton explains that when the nogitsune was first trapped, the nemeton was still whole. It doesn't have the same power now that it's been cut down. Scott asks if there's anything that does. Deaton tells them that when the tree was alive, the wood was sometimes used to contain powerful objects. Lydia makes the connection to the triskele urn and asks if an alpha's claws would be one such powerful object. Deaton asks her which alpha. "Talia Hale." Deaton confirms that the box was made from wood from the nemeton because he carved it himself. Later, two Oni appear and corner Deaton. He attempts to fight by using one of the Oni's swords against the other, but they eventually get a slice in. After the nogitsune is defeated, Deaton touches his chest in relief as they are healed. Later, Deaton asks Scott if he's ever heard the term regression to the mean. He says it's a way of saying that things will always even out. "Like things will always get better?" "More like things can't always be bad." No matter how bad or how good things get, they always come back to the middle. "I'm not so sure that applies to a town like this," Scott says. Deaton laughs and agrees. 
Scott carries Derek inside the animal clinic, and they lay him out on an exam table. "Wow," Deaton says. "Wow. Wow as in 'I've seen this before and I know exactly what to do,' kind of wow? Cause that's the kind of wow we were hoping for," Stiles says. Deaton has no idea what to do. Lydia takes Young Derek's hand and notes that he's really cold. Deaton starts trying to check his vitals. Scott asks if this is permanent, and Deaton replies that he's not sure a medical diagnosis is even adequate. Stiles asks what they should do, and Deaton suggests they leave Derek with him, since there won't be much to do until he wakes up. The mountain ash of the clinic can keep Kate out. Lydia asks why Kate would want to make Derek young again. Deaton can only say that whatever the reason, it must only benefit Kate and be bad for the rest of them. He suggests that they all go home and get some sleep, because it's a school night. "You all need to start taking care of your own lives again." Scott thinks someone should stay. Young Derek squeezes Lydia's hand, and she volunteers. Her grades are good, so she can miss a class or two. The next morning, Lydia wakes up in the Animal Clinic to find Deaton taking Derek's pulse. He reports that it's alarmingly high. Derek isn't as cold as he was. Deaton asks Lydia to keep holding Derek's hand while he cuts into his skin. The wound healed as quickly as he made the cut, which is much faster than usual. He wants to try something else, but while they're getting the syringe, Derek wakes up. His vision is confused and senses muffled. All he can see are their vague outlines and their eyes. Lydia and Deaton keep saying his name, but Derek doesn't recognize them. Frightened, Derek claws Deaton and runs away. Scott and Stiles head over to the Animal Clinic, where Lydia is patching up Deaton's arm. "I don't think he's just younger in body. I think he's younger in mind too," Deaton tells them. Stiles asks where a scared teenage Werewolf would go. Scott says that a wolf goes back to its den, but Derek lives in a loft. "Not when he was a teenager," Stiles points out. They realize that he'll go to the Hale House. He wouldn't remember the fire because it wouldn't have happened yet. Lydia stops Scott and Stiles before they leave and asks what they intend to say to Derek when they find him. Scott thinks he'll have to tell him the truth: that his whole family is dead. "Oh, good luck with that," Lydia replies, nodding. Stiles agrees with Lydia and suggests not telling Derek about his family until they know how to get him back to normal. "I can't lie to him." "Okay, I'll do it," Stiles says. But what Scott means is that Derek is a Werewolf and can tell a lie. Deaton points out that if Derek gets to the house first they won't have to tell him the truth. 
Stiles and Derek have taken Brett to the Animal Clinic and are trying to hold him down so Deaton can make an incision. Brett is seizing and foaming yellow at the mouth. "What the hell is happening to this kid?" Stiles asks. Deaton replies that he's been poisoned by a rare wolfsbane. As they struggle to hold him, Stiles sarcastically asks Derek to "apply a little werewolf strength. Derek glares at him. "Yeah I'm not the only one here with "werewolf strength". Stiles gives Derek a surprised kind of look while Deaton tells them that if they can't hold Brett still the incision might kill him. Brett jerks and throws both Stiles and Derek off. Brett gets up and starts to run, but Peter cuts him off and punches him in the face, knocking him out. Derek watches Peter with cautious awe, and Peter looks at him with glowing blue eyes. "I guess I still have a little "werewolf strength" myself." "Yeah, maybe more than a little," Derek replies, which makes Peter smirk. Derek looks down at the claw marks on his arm, which aren't healing. Stiles kneels next to Brett and claims that he isn't breathing. Deaton cuts the center of Brett's chest, releasing a puff of yellow gas. Peter watches as Derek's wounds heal, and Derek looks incredibly relieved to find out that that power isn't entirely gone yet. Deaton says that Brett will be okay but probably unconscious for a while. Brett starts to mutter something and after a few seconds it's loud enough to recognize as the same mantra Demarco used: the sun, the moon, the truth. Deaton tells them that it's Buddhist, and Peter realizes that their alpha must be Satomi Ito. Later, Scott is brought to the clinic. Scott comes to in Deaton's clinic and sees him looming over him. "I was actually hoping you'd be out for a few more minutes," Deaton says. Scott has one of the berserker's antlers shoved through his midsection. Chris Argent is there and tells him that it's going to hurt before pulling the antler out. It hurts so much Scott lurches to his feet. He asks about his dad and the Sheriff, who are now at the hospital. Scott tells them that it was Kate and the berserkers, but Chris already knows. "They move fast. And they don't leave much in the way of tracks." Scott insists that they have to find Kate because she has Violet, and Violet probably knows where Liam is. Deaton then offers the antler for Scott to get a scent from. After Liam is found, Scott takes Liam to Deaton, who cuts the incision in his chest to let the wolfsbane out. Scott says that he doesn't want to keep watching people die. "I'm not sure you have much choice about that," Chris tells him. Scott thinks he does, but even Deaton warns him that it's a lot of burden to everyone's life in his hands. Scott vows that no one else on the deadpool dies. "I'm gonna save everyone." 
At the Animal Clinic, Deaton is standing out in the rain locking up when he hears someone come up from behind. He flicks out a baton and starts fighting with a hooded figure who uses an emei piercer. After a short spar, they both stop, and Deaton bows. "You could have called Satomi-san," he says. She shows him her red eyes. Deaton and Satomi bring one of Satomi's pack into the clinic. She explains that the sickness starts with fever. Then shifting becomes uncontrollable. They moved into the woods when they started wolfing out for no reason. Eventually they couldn't stand and went blind. Once the Werewolf went blind, they only had a few minutes left before they died. Deaton declares that they need to get the wolf to a hospital. "That's never really been an option for our kind," she says, "unless you know something I don't." "Not something, but someone." Deaton and Satomi bring the dying wolf to Melissa. She asks Deaton if this is what is happening at the school, but he didn't know anyone was at the school because it's Saturday. They get him on a gurney and Melissa tries to get them to a room, but the wolf dies in the elevator. Deaton performs an autopsy on the dead Werewolf. He cuts open his skull and takes a look at his brain, and immediately knows what's wrong. If he's right, though, the Werewolf don't have long. "They're going to die without an antidote." Deaton explains that the illness is a variant of canine distemper. The illness killed 40% of the Yellowstone wolf population. "What's it going to do to our wolf population?" Melissa asks. He says that it's been altered to infect quite a bit faster. "You mean it's been weaponized," Derek says. Satomi says that it infected her whole. "Everyone except for you," Deaton points out. The real question is whether she didn't get exposed or she's immune. Satomi says she used to visit Talia a lot. She asks if he remembers her. "I remember the tea. You always used to bring that tea that smelled terrible." Satomi says that the tea was a gift because Talia loved it. Deaton asks what kind of tea. "Reishi. Wild purple reishi. It's very rare." "It's also a very powerful remedy for sickness." 
Somewhere unknown, Deaton whips out a baton. The wendigo grabs meat hooks, and they fight. As he's about to win, the wendigo informs Deaton that the deadpool is over, so he isn't going to get paid. "I'm not here to kill you, Patrick," Deaton says. "I'm taking you back to Eichen House where they know all about your culinary practices." He then knocks Patrick out with one blow to the head. Deaton takes the tape off Kalissa's mouth, and she asks him if he's a cop. With a slight frown he replies, "Veterinarian." At Eichen House, they wheel Patrick away. Dr. Conrad Fenris works at Eichen House now. It's unclear how long this has been true. He advises Deaton against going to see the man he intends to see. Deaton replies that he came through on his end of their bargain and all he wants to do is talk to him. "The last person that went to see Valack left the room but not the building," Fenris says. Deaton isn't swayed and heads to see Valack anyway. Dr. Valack is behind a plexiglass wall in his cell. He says that Deaton must be important because they don't usually let people get this close. Valack complains that while they let him read, all he gets are trashy romance novels. He tosses the one in his hand onto a pile on the floor. Valack recognizes Deaton by name and says he knows his specialty is not cats and dogs. Deaton says he's there because of what Valack knows about South American mythology, but Valack says he's there to learn about Kate Argent. "You want to know about La Loba. The Bone Woman." Deaton looks thrown for a moment. "I need to know what she did to Derek Hale. And if he's dying." "Why?" "Because of a promise I made. To a woman I loved." Valack tells Deaton to come close, but Deaton replies that he's been advised against it. He's only there to talk, to hear what he knows. "You need to see what I know," Valack says. He removes a band of cloth from around his head revealing a hole. Deaton looks distressed and says that just because Valack trepanned himself doesn't mean he's given himself extra-sensory perception. Deaton looks at the hole and is drawn to it. Valack urges him on, and Deaton seems to move against his will, staring at it. Inside Valack's head, a third eye opens. Deaton gasps awake in a dreamscape of overgrown church surrounded by bone. He pulls an antler out of the altar, and it's covered in blood, like the one they pulled out of Scott's stomach. Outside the dream, Deaton is on a bed in Eichen House and Dr. Fenris is checking on him. Fenris tells his people to check on Deaton every hour. Later, Dr. Fenris decides that Deaton is a lost cause and they have to move him to the sixth floor. Lydia shows up and declares that they're not moving him anywhere. She comes in the room and says she wants to talk to him. Fenris tells her that he's not responding to stimuli so they don't know if Deaton can hear them. "Trust me on this. He'll hear me." Later, Lydia calls Stiles and informs him that Scott's been taken. Stiles replies that it's Scott and Kira but they don't know where. Deaton tells them that they're in Mexico. "And if you want to save his life, that's where you're going too." Deaton looks at Lydia, and she puts her hand over his. 
Dr. Deaton is teaching Scott how to administer shots to dogs from animals. "He's little but his teeth are still sharp," will probably come back later. Scott gives the dog back to his owner and goes back to find Deaton examining the nail. It's a talon from a harpy and shouldn't be able to steal Scott's power. Only a beta of his making should be able to but Deaton believes someone is trying to change the rules of the supernatural world. 
At the Beacon Hills Animal Clinic, Deaton checks Tracy's eyes. They dilate under normal conditions. Her heartrate is 250, which is extremely high. "Evidence of an allogeneic skin graft on the right shoulder." He has no idea what the silver fluid is and comments that it looks like mercury. Malia asks if he can just give her something to kill her. Deaton frowns. "I generally prescribe to a code of ethics that frowns on such measures." Scott tells Malia that they're not going to kill Tracy, but Malia asks how they know she won't kill them. Stiles points out that either way he's going to have to let his dad know they've found her. Deaton grabs a bottle of mountain ash from the table and tosses the contents toward the door, sealing them all into the room. Stiles stares at the mountain ash line across the doorway. He looks very unsettled by it. "Don't worry, Stiles. Tracy won't be able to cross a line of mountain ash. She's not going anywhere." Stiles says that that's what he's afraid of. Deaton reminds him that they will be able to get out without a problem. Scott and Malia will have more of a problem. Malia has never encountered a mountain ash line and tests it. Deaton asks Scott to hold Tracy down so he can try some more invasive tests. He tries to cut her skin with a scalpel and only ends up breaking the knife. "I think you're gonna need a bigger blade," Stiles tells him. Deaton sees something bulge in her neck. He and Malia roll Tracy over. Scott gets a text from his mom that the driver of the prison transport is awake and talking. The driver didn't have a stroke or a heart attack, his body just locked up. "Like he was paralyzed," Stiles says. He realizes that Tracy isn't a werewolf. She's a kanima. They all come over to look at Tracy's back, which has something moving underneath the skin. Suddenly the skin of her back rips open, spraying black ooze, and a tail whips out. It hits Stiles and Deaton first, then Malia. Tracy is up on her feet and claws Scott. She heads out the door, and the moutain ash line break as she crosses it. Stiles is already paralyzed, and Scott stumbles and goes down, too. Stiles asks how she got through the mountain ash, but Deaton doesn't know. Nothing supernatural should be able to cross it. "Scott did it." "Once, and it almost killed me." "We should have killed her!" Malia adds. "Meanwhile, she's probably on her way to killing someone else," Stiles says. Deaton tells Scott and Malia that they will recover from the kanima venom first but they need to focus. Malia doesn't know how to tell her body to heal and starts to freak out. Deaton advises them to think of a body part and visualize it moving. Stiles thinks that his right leg just moved, but Deaton, who can only look at Stiles's legs, begs to differ. Malia's fingers start to move and she's able to get her whole body into motion. Malia struggles to her feet. 
Deaton walks in and covers Tracy's severed tail with his coat. Stiles helps his dad follow Scott and Deaton down to the basement. They find Malia standing over Tracy's body. "It wasn't me," she says. Scott glowers and asks what happened. Malia explains that there were three people in masks. She insists to Stiles that she didn't kill Tracy, and he tries to calm her down. Deaton points out that Tracy isn't changing back to human. "We're going to need to get her out of here." "Absolutely not," the Sheriff responds. "This is a crime scene. We call the coroner." Deaton narrows his eyes. "I think the coroner might be very confused by this girl's severed reptilian tail." The Sheriff seems to have had it. He doesn't care. Deaton thinks he should unless he's prepared to hold a press conference about the supernatural. The Sheriff is clearly unhappy with this, but Stiles agrees with Deaton. Scott tries to play the middle suggesting that at the clinic they might be able to change her back, so they can call the coroner to see something he'll be fit to evaluate. "There is a line that we have to draw," the Sheriff stammers. Stiles points out that they've already crossed that line multiple times. Deaton pleads with the Sheriff to let him help. He caves, and Scott picks Tracy up. Scott and Kira head back to Scott's house. Kira rubs at Lydia's blood on her hands, until Scott takes her hands in his. He kisses her forehead and then kisses her lips. Deaton interrupts them and walks out of hte darkened living room with a bag. He pulls out a bottle. "A werewolf with the talons an eagle. Possibly a shape-shifted known in eastern mythology as a Garuda. Tracy's claws. The unmistakable claws of a werewolf. But a werewolf who also bears the venom and the scales of a kanima." Kira asks what you call that. "Personally, I call it terrifying." But really he's more interested in how Tracy was able to cross the mountain ash. Mountain ash stops supernatural creatures. His theory is that Tracy wasn't created through supernatural means, so supernatural rules don't apply. She was created scientifically. Scott adds that Liam found another hole out in the woods. Deaton suggests the burials are part of an incubation. Kira asks what they're supposed to do. All Deaton can tell her is, "Protect your friends. Protect each other." Scott wants to know how they protect someone like Tracy, who is being used as an experiment. Deaton informs them that he's going out of town for a few days. Kira asks how scared they should be. Deaton says that while he works with the supernatural, he's also a man of science, but something like this rattles the foundation of his beliefs. The rules have changed. 
- ↑ "Visionary"
- ↑ "Wolf Moon"
- ↑ "Pack Mentality"
- ↑ "The Tell"
- ↑ "Heart Monitor"
- ↑ "Night School"
- ↑ "Co-Captain"
- ↑ "Formality"
- ↑ "Ice Pick"
- ↑ "Abomination"
- ↑ "Raving"
- ↑ "Party Guessed"
- ↑ "Fury"
- ↑ "Battlefield"
- ↑ "Master Plan"
- ↑ "Tattoo"
- ↑ "Chaos Rising"
- ↑ "Unleashed"
- ↑ "Frayed"
- ↑ "Currents"
- ↑ "Alpha Pact"
- ↑ "Lunar Ellipse"
- ↑ "Anchors"
- ↑ "Letharia Vulpina"
- ↑ "Echo House"
- ↑ "De-Void"
- ↑ "Insatiable"
- ↑ "The Divine Move"
- ↑ "117"
- ↑ "Orphaned"
- ↑ "Weaponized"
- ↑ "A Promise to the Dead"
- ↑ "Parasomnia"
- ↑ "Dreamcatchers"
- ↑ "Condition Terminal"