Someone is being put in handcuffs while the Sheriff dons a dress shirt and tie. The deputies are taking Donovan out of holding. They walk him out into the main part of the sheriff station, where Tracy's dad is waiting for him. The Sheriff checks himself out in a mirror and gripes about how he should have gotten a haircut. Stiles comments that someone his age should be happy he still has hair to cut. Scott smiles at the Sheriff. "I think you look great." "Well thank you, son I should have had," the Sheriff replies. Stiles looks like he wants to comment but doesn't have anything to say. Sheriff Stilinski gets a bout of doubt and starts to pull his tie off, but Stiles stops him. "Dad, it's one date, okay? The town of Beacon Hills won't implode while you're out with one woman. Or man." "It's a woman, Stiles." Stiles fishes for information on who he's going out with, but the Sheriff tells him it's none of his business.
Parrish leads Donovan and the other deputy out. Tracy's dad tells Donovan that the DA's offer is pretty reasonable. The deputy tells them to talk in the van and tries to hurry Donovan along, but Donovan resists and turns to talk to Mr. Stewart. Parrish asks Stewart if they're going ot have problems. Mr. Stewart tells Donovan that the offer is for 3-5 years. He wants to get in the van and discuss a plea bargain that would get him out in two. Donovan starts shouting the Sheriff's name, and the Sheriff, Stiles, and Scott come out of the office to see what the commotion is. "I'm going to kill you!" Donovan shouts. The Sheriff calmly replies that he isn't shocked because Donovan's outbursts are well documented in his Anger Expression Inventory. Donovan replies that he's not angry like he's going to throw a brick through his window. "I'm angry like I'm going to you, I'm going to get a knife, and I'm going to stab you with it until you're dead. And when you look at me and you ask me why, remember right now. Because this is why." Mr. Stewart rolls his eyes shut at the stupidity of his client. Stiles breaks the silence. "Wow, that was awesome. That was awesome. That was great. Can we do one more? Give us another one maybe like Christopher Walken this time, you know." No one says anything as Stiles defuses the room, telling Donovan that he can work on his delivery while he's in prison. Donovan tries to lunge at Stiles, but the deputies hold him back and the Sheriff yells at them to get him out of there. Scott asks Stiles what an Anger Expression Inventory is, and Stiles explains that it's a test you take when you're applying to be a deputy. Scott is surprised to learn that Donovan wanted to be a cop. Stiles quips that at least now he's getting the full law enforcement experience.
A new nameless deputy is driving the prisoner transport van. Mr. Stewart sits up front while an armed deputy sits in back with Donovan. Stewart yells at Donovan for totally screwing over his chance at a decent deal now. The deputy that's driving seems to be having some difficulty as the van starts going faster. Stewart asks him to slow down, and the deputy holds up his hand. He's in pain and thinks he's having a heart attack. The van flies around a turn, and everyone starts yelling. The driver can't move his legs. Mr. Stewart grabs the wheel, and Donovan hollers at him to hit the brakes. Donovan looks up to see holes in the ceiling that are dripping clear fluid. The van continues to swerve around, crashing into the sides of an underpass. Mr. Stewart is finally able to hit the brake, and the van comes to a stop. In the moment of calm, they hear something on the roof. It turns out to be Tracy. She growls at her father. She punches through the window, hitting the driver and splattering her father with blood. The deputy in the back opens fire on her. Donovan jumps out the back of the van and makes a run for it while Tracy attacks the other deputy. Mr. Stewart comes out of the van and faces his daughter. "Don't worry Daddy. I won't let anything happen to you ever again," she says. Then she kills him. Donovan trips and falls, then looks up to see The Surgeon coming at him. The other Dread Doctors appear behind him and grab him. The Surgeon drills into Donovan's ear and fills him with the silver fluid.
At the sheriff station, Stiles tries to get his car to start. He looks over at Scott and says, "It's anxiety." "What is?" "The chemo signals? I'm well aware of how you all monitor my emotional state." The car still won't start and Stiles punches the steering wheel. Scott asks him if he's okay. Stiles explains that he got a message from Braeden a few hours ago. He hands Scott his phone to show him pictures of the Desert Wolf's handiwork. "The Desert Wolf did this?" "Yeah. And I'm the one who's been pulling on this thread." Scott suggests maybe he stop, but Stiles doesn't think it's up to him. He tries the car again and it starts.
Meanwhile, the girls are trying to teach Malia to drive. Malia adjusts the mirrors, and Kira tells her to place her hands on the wheel at 10 and 2. Lydia corrects her that it's now recommended to use 9 and 3 because at 10 and 2 a deployed airbag could break your thumbs. "Mine would heal," Malia offers. Lydia tells her to save her strength and try not to destroy her beautiful new car. Malia grips the wheel extra tight as she has another flashback to the car crash that killed her mom and sister. She's viewing it from the outside, seeing a bloody hand. Malia shakes it off and starts the car. Kira tries to encourage her until Malia tells her to shut up. Malia drives all over the road and then off the road while Kira asks her to please stop driving into the woods. Malia asks what the beeping sound is and Lydia informs her that the car is telling her not to run into the tree. At the last moment, Malia turns the wheel. She starts driving in a circle in the middle of the road. Lydia suggests she try the gas a little harder, and they take off. Malia follows Lydia's directions, which she claims is toward the school so they can finish in the parking lot, but Kira points out that the school is the other way. Lydia says they need to keep going. She gets a far away look in her eyes as she zeroes in on death. They find the prisoner transport van where Tracy killed her father and call 911.
Not long after, the sheriff's department is there, along with Scott and Stiles. The Sheriff asks Scott if Donovan was a werewolf. Scott doesn't think so, but he doesn't seem sure. Sheriff Stilinski asks Scott if he can find Donovan for them. He hands Scott a radio and tells him to keep it on channel 2. Scott takes off running. He jumps off a wall into a Dumpster and adds a gratuitous forward flip for good measure to jump to the ground. His eyes glow red as he goes on the hunt. Back at the crime scene, Stiles suggests to his dad that it wasn't Donovan. Based on his current suspicions, Stiles must be thinking Theo, who is up on the overpass watching them. Scott tracks Donovan to an abandoned warehouse. Donovan attacks, and Scott slams him to the floor. He reports in that he found him and that he keeps saying, "Tracy." Stiles thought it would be Theo. "Tracy who?" the Sheriff asks. "Stewart," Lydia supplies, sounding resigned.
The next day, everyone meets at the school to talk. Lydia explains that she was having night terrors. Stiles quips that now Tracy is the night terror since no one can find her. Scott starts to say that he knows they're all tired and miserable, except for Mason, who is looking at all of them with awe. He motions at Kira. "You're a kitsune. I don't even know what that is!" Stiles admonishes Liam because while they said he could tell Mason they didn't say he could invite him to the inner circle. Scott brings the convesation back to Tracy. They can find one lone wolf. Stiles wants to know what they do when they catch her. "I say we put her down," Malia says. Everyone looks at Scott, who suggests they concentrate on catching her first.
In lock-up, Donovan is feeling the effects of the Dread Doctor's injection. He tells the Sheriff he wants his lawyer. "Your lawyer's dead." Donovan asks for another lawyer. The Sheriff tries to get him to talk about what he saw, but Donovan refuses. As the Sheriff leaves, Parrish stops him. They know why they couldn't find Tracy last night. She was busy killing her psychiatrist. The Sheriff tells Parrish to inform Scott but tell him that they shouldn't get into it yet. Parrish asks if they should be putting Scott on the payroll.
Stiles shows Malia the picture he got from Braeden. He explains that he wanted to show her first but lacked self control. The Desert Wolf killed a room full of men that according to Braeden were pretty bad. "So they deserved it?" Malia asks. Stiles agrees sort of. "Not sure anyone deserves that per se." Malia comments that at least they know the Desert Wolf is good at her job.
In AP Bio, the teacher hands back their tests. Scott got an 86. The girls smile proudly at him, as Mrs. Finch asks Scott to lead the class in a review of last night's reading. Liam appears outside the classroom and tries to get Scott's attention. Mrs. Finch keeps trying to get him to focus. Scott taps his ear to indicate that Liam should just talk. "She's here. She's in History class right now. Tracy." Theo is listening, too.
In Mr. Yukimura's History class, Tracy is sitting at the back, gripping her desk. She doesn't even belong in the class because she's a senior. She scratches the underside of the desk with her claws and breaks the desk in half. Hayden looks over at her, concerned. She notices that Tracy's feet are dirty and she isn't wearing shoes.
Liam pulls the fire alarm to get everyone out. Hayden tries to get Tracy to leave, but Tracy grabs her arm. Scott and Liam come into the classroom while everyone files out. Tracy sees the Dread Doctors where Liam, Scott, and Mr. Yukimura are standing. Tracy stands as Scott comes closer and squeezes her claws into Hayden's arm until she bleeds. "Tracy, let go," Scott says. "They're coming," she replies. "They're coming for all of us." And then she collapses. Silver fluid leaks out of her mouth. Scott, Mr. Yukimura, Stiles, and Malia get Tracy out of the building. Hayden asks Liam where they're taking her. "Hospital, I guess." He sees Hayden's bloody arm and asks her if she needs help getting to then nurse's office. "I think I'll make it," she tells him. In the bathroom, Hayden washes the blood off her arm and discovers there are no wounds.
Liam catches up with Kira and Lydia. They're taking Tracy to the Animal Clinic to see if they can figure out what's wrong with her. Lydia replies that what's wrong with her is that she killed two epople. Her father and "according to Parrish, her psychiatrist." Kira asks if there's anyone else they can talk to, her mom or any family. Lydia suggests an alpha. If she's a werewolf, she must have an alpha. "Anyone know if a new one's moved into Beacon Hills?" "No, but there is an old one," Kira replies. Liam is sent to talk to Brett because he's a member of Satomi's pack.
Mason and Liam find Brett on the lacrosse field at Liam's old school. Mason watches Brett play, shirtless, and gawks. "So he's a werewolf, too?" "Yep." "This just gets better and better."
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.
Kira and Lydia are at Tracy's house. Kira asks if this is a crime scene, and Lydia scoffs, only to see crime scene tape across Tracy's bed when they go in. They don't know what they're looking for. Lydia is just following a feeling, which Kira points out usually leads to dead bodies. "Well let me know if you find one," Lydia quips.
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.
Meanwhile, Mason and Liam show Brett a picture of Tracy. "Cute. Never seen her." Liam asks if Satomi could have turned her without Brett knowing. Brett says that after the dead pool she's not really doing much recruiting. Mason asks if that's how it works, alphas just go around biting people. "Or you can be born like me and my sister. Satomi took us in after our family died in a fire." Liam looks more closely at the photo of Tracy and realizes that he's seen her necklace before, when he fell in a hole in the woods.
It's evening and Lydia and Kira are still looking around Tracy's room. Kira finds a dreamcatcher in a box. It was a gift from her dad, who was trying to help her with her night terrors. Lydia recalls that there have been cases of people murdering their entire families while in a night terror. It's called homicidal somnambulism. She thinks Tracy could still be in a night terror.
While examining Tracy, 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.
In the woods, Liam, Mason, and Brett search for the hole that Liam fell in. Mason falls into a hole but there's no necklace. Mason says that the hole doesn't look like a sink hole. There are handprints and dirt on the edges. They realize that someone was buried there. "Intense," Mason says.
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. Stiles tells her to wait for the rest of them, but Malia is not interested in waiting. Tracy has a scent, so Malia knows she can find her. "Malia! Save her," Scott says, and Malia grimaces at him.
Kira and Lydia piece together that Tracy has been killing people who tried to help her. Maybe that's why she was at the school. The other person that tried to help her is Lydia's mom. Mrs. Martin is at the Beacon Hills Sheriff Station to go on a date with Sheriff Stilinski. Natalie tells the Sheriff that she's glad he didn't have to cancel again, and he smiles back at her. The Sheriff glances into the station to see Deputy Clark collapsed at her desk. "I can't move," she tells him. The other deputies are also incapacitated. Lydia and Kira burst into the station to warn them, but Tracy is already there and on the ceiling.
Liam searches the hole himself and agrees that the necklace isn't there. He doesn't think this is the same hole he fell in earlier. "Then who crawled out of this one?" Mason asks.
Donovan is still sitting in lock-up. He opens his eyes and silver fluid flicks sideways across them like a nictitating membrane. He rubs his face and then hears gunshots. The Sheriff fights Tracy but she slices him and knocks him down. Kira gets our her belt sword and they fight. Lydia tries to hid eand urges her mother to run. Tracy attacks Lydia, slicing deeply into her right side, and Lydia falls. Kira jump up onto a desk and her kitsune aura comes out. She attacks and slices off Tracy's tail. Tracy makes a run for it, while Kira's powers overwhelm her.
Back at the Animal Clinic, Theo helps Scott to his feet, then Stiles. Theo offers to help. "It doesn't have to mean I'm part of the pack. Like you've accepted me or anything like that." Scott has trouble making a decision.
Malia catches up to Tracy at the sheriff station. The Sheriff tells her to be careful. Lydia calls to her with a shaky voice and tries to convince her that her wound isn't as bad as it looks. She explains that Tracy is dreaming and tells Malia to get Tracy to understand that she's not asleep. The Sheriff then tells Malia that they're in the basement. Malia follows the blood and finds Tracy dragging Mrs. Martin. Tracy tosses Natalie aside in order to fight. Malia gets Tracy on the ground, grabbing her arms and pinnign her neck with her knee. As she chokes, Tracy shifts back to herself and Malia lets her go. She tells Tracy that she's isnt' dreaming and everything is real. "What's happening to me?" Tracy asks. The Dread Doctors appear and inject Tracy with more silver fluid. One slams Malia into the wall and holds her there to keep her from interfering. "Condition is terminal," The Surgeon says. Tracy falls down dead, and the Doctors leave. They disappaer from the hallway as Malia watches.