Parrish is in his living room on the couch, playing with a deck of cards. He keeps flipping one over, revealing the Queen of Diamonds.
In a flashback, Lydia and Parrish are at the sheriff station, and Lydia is playing with a lighter. "You gonna do a magic trick?" Parrish asks her. She gives him a critical look and replies that she isn't but he is. Parrish comments that the only trick he knows is with a playing card. "Well, this one involves a lighter and your hand." Parrish tells her that that sounds like assault, and Lydia admits that it's a little dangerous but not nearly as dangerous as that time he was set on fire in the police car. He was unscathed, except for having to buy a new uniform. Lydia looks at him seriously. "Give me your hand." Parrish continues to make jokes. "Remind me what the trick was." "Not minding." He holds out his hand, and Lydia holds the flame under it. After a few seconds, Parrish jerks his hand back, and Lydia laughs. "You can last longer than that." The innuendo is clear and prompts him to try again. Lydia tells him that she wants him to do something different as she takes his hand in hers. She tells him not to think about the flame or the heat or it hurting. She instructs him to not even look at his hand. They try again. This time Parrish stares at Lydia, and the smoke starts to rise from his hand. He zones out, until Lydia yelps in pain because her thumb was too close to the flame for too long. Parrish turns over his hand and swipes through the soot on it. There's not a mark on him. Lydia tells him that when he was looking at her, his eyes drifted. He was thinking about a dream he's been having off and on for six months.
Parrish is naked and covered in soot, walking in a forest on fire. He's carrying the burned body of a woman that he can't identify. He takes the body to a clearing, to the nemeton. Lydia recognizes it by his description and informs him that it's a real tree. The nemeton was a sacred meeting place for Celtic druids. Parrish replies that he's never seen the place, so how could he be dreaming about it. But Lydia informs him that that's why he's in Beacon Hills, because it called him there. The nemeton is a beacon for supernatural creatures and might make them more powerful. Lydia asks how the dream ends, but Parrish says it ends when he puts the body down on the stump. In the dream, Parrish sets the woman on the nemeton and sits down next to her. The flashback ends.
Parrish continues to flip the cards, only this time he goes from a Queen of Diamonds to a burned Queen of Diamonds, and it's revealed that he has two cards. He remembers more of the dream. There are bodies all around the nemeton. And as he sits down, he starts to burn. There are flames all around the nemeton and the dead. Parrish touches his forehead with both hands, like he's stressed, and then his eyes glow, and he looks up calmly.
At the sheriff station, Donovan is in holding while Tracy and Malia have been fighting downstairs. He bangs on the bars to be let out. "C'mon Gabe, let me out! Come on!" Donovan says, calling to one of the deputies. The Dread Doctors approach the cell and unlock the door without touching the card reader. One of them has a cane. Scott, Stiles, and Theo run into the sheriff station. They see blood on the floor, and Scott rushes in. The Sheriff is already trying to get to his feet when Scott rushes to help him. Stiles finds Kira and Lydia in the office, with Lydia bleeding badly. Theo pushes past him and uses his belt as a tourniquet on Lydia. Deaton walks in and covers Tracy's severed tail with his coat. Ms. Martin is safe and comes back up from the basement nearly in tears. She sees Lydia and runs to her side. Stiles has been staring at Lydia this whole time. It takes Scott a few tries to get his attention. Theo and Lydia both tell Stiles that it's going to be fine, and she tells Stiles to go save Tracy.
There are already ambulance sirens in the background. 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.
In the Doctors' secret lab, Donovan is strapped down to a table. They manhandle him, and The Surgeon declares, "His condition looks promising." One of the other Doctors then grabs a set of pliers and rips out three of Donovan's teeth. He grows wendigo teeth on his own after that.
Lydia is at Beacon Hills Memorial being taken for surgery. Lydia comments that her spleen is injured. She begs her mother not to talk about what she saw. Ms. Martin replies that alls he saw was some lunatic girl trying to kill everyone.
Scott and Liam burst into the hospital. Liam is telling Scott about what he found in the woods and confirms that Tracy was buried alive, then crawled out. They found a second hole, but Liam doesn't know who was buried in that one. He thinks they need to find out, though. Melissa comes out to tell Stiles, Scott, Kira, Theo, and Liam that Theo's tourniquet probably saved Lydia's life. Stiles doesn't say anything to Theo, but he acknowledges the good Theo has done for them. Lydia is about to go into surgery, so Melissa asks if there's any supernatural details they need to know about or do they just treat Lydia like a wounded human. Kira informs her that Lydia was cut with Tracy's tail, although it is unclear what difference that could make. Malia insists that it wasn't just Tracy, there were guys in masks. Stiles and Scott look torn between being worried and not believing her. In the operating room, Melissa asks Lydia to count down while they knock her out. As Lydia starts to go under, she hears the sounds of the Dread Doctors and starts to see them.
Stiles and Malia go back to Stiles's room, where he adds notes to his crime board: Masked Killers and Tracy Stewart. Malia looks at the othe rquestion Stiles has written there: Who is the Desert Wolf? She gets up and erases it. She and Stiles exchange a meaningful look.
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.
Post-surgery, Lydia wakes up the following day to find Parrish sitting in her room. She asks him what he's doing there. "Officially, I'm here to gather eyewitness testimony. Unofficially, I'm trying to find something to watch. But the only thing that comes in is this kung fu movie." Lydia asks Parrish if he knows how to fight. He says he knows a little ju-jitsu because the army taught him close quarters combat. She asks him to teach her. Parrish agrees.
In AP Bio, Mrs. Finch asks them what could account for the 0.1% difference in DNA between humans. She calls on Theo. He answers, "Nucleotides." This does not actually answer the question she asked. Scott is looking at a list of all the things they've encountered so far. Kira asks if there can be more than one species in the same DNA. The answer is no, but there can be multiple sets of DNA in the same individual. This is called a chimera. Sydney offers that the term come from Greek mythology about a lion with a goat's head coming out of its back and a tail that ends in the head of a snake. Mrs. Finch tells her that she's right and then asks if she'd like to read the full wikipedia entry off her phone. Scott notes down the term chimera, while Mrs. Finch goes on to talk about mutation. DNA is a fragile molecule. Mrs. Finch asks Scott if he missed the assigned reading. "Kind of." "Kind of or yes?" "Mostly yes." She then offers the class drop forms. Mrs. Finch hands out a few forms to students she thinks should fill them out. Class is dismissed, and Scott takes a form. The teacher doesn't look pleased.
At the sheriff station, they watch the video of Donovan in the cell. The video cuts out during the time when Donovan escapes. Deputy Clark is in on her day off because Donovan is missing after having threatened the Sheriff's life. She's not taking a day off unil he's caught. The Sheriff isn't concerned. He thinks Donovan is running as far as possible, as fast as he can.
Donovan continues to struggle against his restraints. "You're lucky they're allowing me to talk to you," Theo says, as he walks into the lab. "They don't usually do that." Theo explains that the Doctors believe in numbers and results and they will quickly decide if Donovan is going to die. Theo has Donovan's aptitude test from when he applied to be a deputy. The multiphasic personality inventory assesses abnormal behavior. Theo seems pretty comfortable with this terminology, suggesting he knows far more about it than a normal teenager would. Donovan scored high on the psychopathic deviate scale. Theo slaps the file against Donovan and tells him that that's bad. And that they're not even going to get into his Anger Expression Inventory. The point is the conclusion at the end: not suitable for law enforcement. Theo tosses the file away and says that it sucks that Donovan will never get to be a cop like his dad. Theo tries to sell Donovan on the transformation they've done to him. "You've got something else now. Power. Real power. Strength, speed, heightened senses." He cranks the table so Donovan is sitting up more and takes the restraint off his head. Theo knows that Donovan wants to go after Stilinski, but he has a better idea, a way to hurt him more than just physical pain. He sends Donovan after Stiles.
Scott and Kira are in the library, and Stiles and Malia join them. Stiles wasn't able to get in to see Lydia because she's in the ICU and only family is allowed. They did, however, come back with the bestiary. Kira asks if there's anything about a half-werewolf, half-kanima. "Chimera," Scott says. He explains the term and tells them that Liam found two burial sites, so there's more than one. Kira opens the book to the page on wendigos.
Someone in the hospital is screaming. Melissa and Liam's dad rush to check on him and don't immediately see what's wrong. Melissa checks the kid's arm and the skin is melting off. His whole forearm is an exposed wound.
That night, Mason and Liam go to a club. Mason asks Liam to put his phone away. Scott can always howl if he really needs him. Liam complains that he feels like he should be helping. "You are. You're my wingman tonight. And considering the state of my dating life, I need a wingman, a co-pilot, and a really hot flight attendant." Mason convinces Liam to go in. They get to the door, and Hayden opens it. She gives Mason a harsh look and tells him that she didn't say she'd let Liam in. "You said I could have a plus one." "I didn't say plus Liam." "I'm his flight attendant," Liam says. Hayden scowls at him and he corrects to wingman. Mason bribes Hayden with $50 to get Liam in. The club is Sinema, and it's a mostly gay club. Liam comments that they don't look old enough to be there. They spot Brett dancing with a woman and then a man. Liam asks if the club is mixed and Mason replies, "Ish."
In the library, Stiles is asleep on a pile of books. Malia is still awake, clicking her pen as she looks thoughtfully at their research. The motion of her pen reminds her of the motion of the needle that The Surgeon used to kill Tracy. Malia sets the pen down and informs Stiles that she's leaving. He mumbles something back. She tells him to wake up and go home and that she'll meet him there in a bit. Again, he mumbles.
Hayden is serving drinks at Sinema. The bartender takes a drink from one of the test tubes, and she admonishes him that she has to pay for them out of her own pocket. The bartender, Phil, apparently gets drunk while on the job. Hayden takes the drinks and stops as she walking to count her tips. She complains to herself that she's never going to make enough, and Liam overhears it. He watches her go, curious, and then spots Mason and Brett having drinks together. Suddenly, Liam's senses come into sharp focus and he follows the sound of incongruous footsteps.
Scott and Kira arrive at the hospital, having been called by Melissa. She leads them to the room with the kid who is still screaming from the wound on his arm. Scott listens to his agony for a moment before deciding to try to help. The kid is strapped to the bed with a bandage over the wound. Scott grabs the boy's hand and black veins swarm up his arms. Scott nearly passes out from the pain. Kira and Melissa have to pull him away. It works, though. The boy stops screaming. Scott asks to see the wound, and Melissa shows him. The lab says that the wound was made by scorpion venom. The weird part is that a sting that bad should have killed him hours ago and the scorpion that stung him would have been 10 feet tall. Kira hopes there isn't a giant scorpion running around Beacon Hills. The boy is able to tell them that it was Lucas, his boyfriend.
Liam is asking Brett if he noticed anyone off in the club. Brett isn't sure because it's Beacon Hills. It's always possible someone is a werewolf. Liam explains that whatever he sensed felt off. "It felt wrong." Mason asks Brett if he knows the guy that keeps looking over at them. It's Lucas. Lucas gives Mason a sly smile, and spines come out of the back of his arms. Liam continues to follow his instincts and notices that Lucas has become a danger.
The boy in the hospital, Corey, tells Scott and Kira how he got stung. He says that he and Lucas were taking it slow, but it wasn't him, it was Lucas that wanted to, but today he was like a different person. He was aggressive and super confident. "We were just kissing, and then I felt this sharp sting on my arm." He saw Lucas's eyes turn black, as well. Lucas apologized and then said he's see Corey at the club later. Kira asks what club, and Corey directs them to Sinema. Liam is searching through the club when he collides with Hayden, making her drop all the drinks. They were $10 each, so he owes her $200.
Mason goes into a back corner with Lucas. Night of the Living Dead is being projected onto Mason's shirt. He comments about it. Lucas asks how it ends, and Mason tells him that the zombies pretty much win and the good guys die. "So I guess it's better to be one of the bad guys," Lucas replies. He moves in on Mason and starts kissing him. Spikes grow out of Lucas's spine.
Kira asks if there's even a myth for a half-scorpion half-werewolf. "Sumerian," Scott supplies. He saw something about it in the bestiary. They arrive at the club and go inside, setting off an alarm. Scott loosk around, confused, while Kira grabs a piece of her belt and uses it to break the alarm. Scott declares his love for her badass self.
Lucas kisses Mason some more, right up until Brett grabs him and flings him across the room. Brett tells Mason to run. Kira follows Scott into the club and says that he did it again. He did something that changed everything without even realizing it. He said those three words. Scott hears roaring from Brett and Lucas fighting. Lucas slices Brett across the stomach, and then Liam comes flying in to tackle him. Scott and Kira find Lucas wrestling with Liam. "You're a little late!" Liam yells. Scott attacks and manages to get Lucas off Liam, but Lucas quickly tosses him aside. Kira uses her belt sword and joins the fight.
Malia is at Tracy's house, looking through her room. She checks out the drawings on her wall. Then she spots Tracy's wallet with a novel underneath. The novel is by T.R. McCammon. The note on it reads "Here's the book you asked for. Cheesy stuff, but still a fun, scary read." The title of the book is The Dread Doctors, with drawings of each of them just as Malia has seen them.
Kira continues to fight Lucas, while Mason tries to help Brett. Liam catches Lucas off-guard and slams him to the ground. Lucas seems to come back to himself, but in the moment of calm, Kira's kitsune spirit comes out. "Watashi wa shi no shisha da!" she shouts. It means, "I am a messenger of death." And she makes to kill Lucas. Scott grabs her arm to stop her, and they stare at one another. When it's clear that everyone is okay, Scott asks Liam to help him get Lucas out of there. They start to pick him up, but he's shot in the chest with a dart. The Dread Doctors are up in the rafters. Scott demands to know why they killed him. "His condition was terminal." Scott asks what that means. "Failure," the Doctor replies. The Dread Doctors disappear as quickly as they appeared.
They bring Lucas to the hospital morgue. Melissa is sure they'll come up with a reasonable explanation for the stingers in his arms, which is somehow better than trying to explain a tail. They close him into the fridge. Scott is upset because he thinks he should have done better, predicted that this would happen. Melissa tells him that his grandfather used to have a saying about the word should. "You know what you're doing when you say the word should too often? You're should-ing all over yourself." Scott smirks. Melissa can't tell Scott not to do something about it, because he's got the power to do something and cares enough to try. All he needs to do is ask himself what he's going to do. Scott thinks about it. "I'm going to find out who did this. And I'm going to stop them." They leave the morgue, and someone new walks in. Parrish opens the fridge and removes Lucas's body.
Later that night, he's walking through the forest toward the nemeton carrying Lucas's corpse. Parrish sets him down on the nemeton and engulfs them both in flames.
Stiles is finally trying to leave the school library, but the Jeep's engine is smoking. He has a wrench and duct tape, and tries to fix it. While he's working on it, Donovan comes up behind him. Donovan has a lamprey mouth in the palm of his hand and attaches it to Stiles's shoulder.