A man in a lab coat walks through his laboratory, which is lined with mountain ash. As he sits and takes notes, someone behind him snarls. There's a werewolf trapped on a medical bed, dying. Black ooze drips from his eyes. The scientist plays back a message on a tape deck from the Benefactor. As he drinks his tea, the tape explains to him how to enter his information into a website that will allow him to receive wire transfers.
The scene shifts to Scott and Stiles listening to the tape that was in Garrett's bag. It says that they will receive a new IP address to connect to after every wire transfer. The tape stresses that visual confirmation is always required for payment. Stiles has never made a wire transfer. Neither has Scott. And Scott doesn't understand why someone would pay so much money to have them killed. All Stiles can say is that someone clearly wants them dead very badly. Scott takes the stacks of money and starts putting them back in the bag. Stiles asks him what he's doing, and Scott reminds him that they've got the PSATs in the morning. "No, I meant the money. $500,000. Do you know how much money that is?" "It's $500,000--" "It's half a million dollars, Scott. What are you going to do with it, just slide it under your mattress?" "I have to talk to Derek. The money's his," Scott points out. Stiles replies that the money is Derek and Peter's, and he thinks they should proceed with caution. " It's not that Stiles doesn't think they should tell Derek, just that telling Derek also means telling Peter, who is a homicidal killer. "So we should give Derek his money back, but not Peter?" Scott asks, trying to clarify. That isn't Stiles's point either. Before he can really nail down what he means, Malia runs up the stairs to Scott's room and Scott shoves the money bag under his bed. Malia reports that she and Derek found Satomi's pack but they're all dead. She's wet. Apparently it started to rain. Stiles asks where Derek is.
Derek carries Braeden into the ER. "She's been shot! I think she's dying," he says to Melissa.
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.
The following morning, Stiles, Scott, Malia, and Kira are in line to take the PSATs. Kira asks where Lydia is, and Stiles explains that she took the PSATs freshman year. Malia asks if this means she can take the test some other time. Scott tries to reassure her because she studied harder than any of them. "That doesn't mean I'm going to do good," she says. "Well," Stiles corrects. "It's do well, not good." Malia takes this as further proof that she's going to fail. Scott says that she's doing this because while they're trying not to die they still need to live. Scott wants to go to a good college. Kira thinks they can all survive three hours.
As the students come in to get their tests, they mark their presence by leaving a fingerprint using an ink pad. Mrs. Martin collects all their cell phones. They all sit, and Stiles opens up his test and starts reading the first page. Simon, the proctor, asks them not to open their booklets until they are instructed to do so, and he quickly closes it. The proctor explains how long the test is and how many critical reading sections there are. There are supposed to be two teachers monitoring the exam, but only Mrs. Martin is present. Coach Finstock is also supposed to be there. Mrs. Martin goes to call him again but realizes his office is just down the hall so she checks in. She finds him passed out on his desk. When she lifts up his head, she thinks he's passed out drunk. "Oh, Bobby. Fifteen years sober and you fall off the wagon at school?" Mrs. Martin, Natalie, tries to wake him up, but she can't. She says she'll bring him coffee during one of the breaks. She returns to the classroom and informs the proctor that Mr. Ken Yukimura is upstairs grading papers, so she'll get him instead. The proctor says that they have to start now, so they can ask Mr. Ken Yukimura during the first break.
The test begins, and everyone starts filling in answers. Stiles sees one in particular that makes him drop the pencil from his mouth and scratch his head in distress. Malia is so upset she takes her jacket off. Just then, another student falls out of her seat. Natalie rushes to Sydney's side to see if she's okay. Sydney claims she just got dizzy, but Natalie spots a nasty red rash on her arm. Simon asks if he needs to stop the test, but she says no. Natalie then slips out of the room with her cell phone and informs Simon that no one can leave the room. She heads into Coach's office and uses a tissue to touch him as she looks for a similar rash. He doesn't have one on his wrist, but his back is covered. Some students arrive and try to come into the building, but Natalie shouts at them to leave. She locks the door, and when everyone comes out to see what the shouting was about, she asks them to go back and sit down. When the classroom door closes, she calls for the number for the CDC. Scott can hear her and knows something is really wrong. Soon, a team in hazmat suits enters the school and starts setting up quarantine. The Sheriff arrives outside and questions Dr. Wentz about what's going on. She says she hopes it's a false alarm but the details they got made them concerned enough to set up quarantine. They're going to need his help in making sure that no one goes in or out of the school. "My son is in there," the Sheriff says. She asks him if that's going to be a conflict. "Conflict? No. Stressful? Yeah."
Inside, Natalie tells Scott that they need to isolate the sick and wait for instructions. If she's wrong, they'll be out of there pretty quickly and she will just be the crazy biology teacher who panicked for nothing. She puts a blanket on Sydney and leaves Scott and the girl to talk. Scott tries to comfort her, thinking she's upset about dying, but Sydney explains that she's worried about not qualifying for the National Merit Scholarship because the PSAT was interrupted. She can't afford to go to college otherwise.
Stiles tells Malia and Kira that he bets the CDC thinks it's smallpox. Simon explains that smallpox was eradicated in 1979. It was one of two viruses ever eradicated. The other was rinderpest, which killed cows. Stiles asks if they should be comforted, and Simon replies, "Unless it's something worse." Malia listens to the chatter outside and reports that there's a lot of activity, plus the Sheriff is there. Stiles thinks he should call him, but Simon points out that they will have cut off cell service to keep them from being able to spread panic. "Looks like we're all just going to have to wait here and see what happens."
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 werewolves 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." Melissa walks down the hallway, passed a girl in a red jacket, crying. She goes into Braeden's room and gives her an injection. Derek asks what it's for. "Naloxone. We need to wake her up." Derek thought Braeden needed to rest. "That was before I found out the CDC just put the high school under quarantine with Scott and Stiles still in there." Braeden gasps awake, and Melissa explains to her where she is. She asks Braeden what happened to the other pack she came across. Derek breaks in, "I told you they were poisoned." "No. No, they were infected," Braeden says. "It was a virus designed to kill werewolves. And it did. It killed them all."
Back at the school, Natalie tries to get Scott to come out of the bathroom. He's standing over a sink trying to control his shifting. His fangs are out, and he looks ill.
Lydia is up at the lake house in the white room with a box of Meredith's things. She places the items around herself in front of the record player and turns the player on. She tries talking to Meredith. "I dontt know how to do this. I'm not a psychic. Apparently I'm not much of a banshee either." She doesn't know what she's supposed to ask, just that she wants to help her friends. "But if I have this thing, it's gotta work some of the time. It's gotta help someone." She's on the edge of tears, possibly thinking about how her powers didn't help Allison. After a moment of silence, Lydia realizes that maybe what she really wanted to say was, "I'm sorry. I wish I could have helped you. I'm sorry." She turns the record player off and starts putting away Meredith's things. She picks up a photo and realizes that the photo is of Meredith in this same room.
At the school, Mr. Ken Yukimura finds Scott in the boys locker room trying not to wolf out. "Get Stiles," Scott tells him. Everyone else is waiting in line to have the CDC take blood samples. Malia takes this opportunity to ask Kira if she knows what Scott and Stiles are hiding. Kira thinks it's about Malia being Peter's daughter and acts cagey. Malia is clearly attempting to have a normal conversation like this is something she knows how to do. Kira says that she thinks if they hide stuff they have a pretty good reason. Malia gives up the pretense and asks if she knows what they're hiding in the bag under Scott's bed. Kira was not expecting that. "What? No, I've never been under Scott's bed. Or in it. Just on it... wearing clothes." She stops herself from talking and turns to Dr. Wentz calling her name. Dr. Wentz tries to get a blood sample but instead she gets a nasty shock from Kira's foxfire. Dr. Wentz rushes out of the school in case her suit was breached. It wasn't. Rafael McCall asks her if she knows what they're dealing with because his son is in there. She advises Sheriff Stilinski bring McCall up to speed. McCall asks if he thinks smallpox is possible. The Sheriff replies that he doesn't think the Orphans were the only professional killers in Beacon Hills.
In the locker room, Mr. Ken Yukimura checks on Scott and Malia. Malia can't get her claws to go back in. Stiles says that they have to quarantine them from the quarantine so no one can see them. Kira asks where. "What if they get violent? Like on a full moon?" They can't use the locker room, or a classroom. Apparently the basement now has too many ways out, even though it was the perfect place to lock Boyd and Cora when they were uncontrollably violent. Stiles suggests they use the Hales' vault. They figure that since the Hales built escape routes into their house, they may have built one into the vault. They get some blueprints, and Stiles pinpoints a likely spot for a second entrance in the hallway in the basement. Stiles gets dizzy and pulls up his sleeve to reveal a rash like Sydney had. Mr. Ken Yukimura says they're all getting sick and looks at Kira. She says she doesn't feel sick. "I think it's affecting your differently, neurologically. I found your test answers here in a pile with the others." He shows her the answer key, but half her marks are outside the bubbles.
They all head down to the basement. Stiles finds a lock like the one outside behind a shelf surrounded by a large triskele. He and Scott agree without speaking that Malia should open the door with her claws in case it requires a Hale. Scott claims he can't make his come out. She agrees but asks what the secret is they've been hiding. She asks how much she's worth on the list, and they tell her $4m. She doesn't think that's a problem because Scott and Kira are worth more so they will be taken out first. Malia opens the door to the vault and they all head in. The door closes behind them.
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.
Back in the vault, Stiles is cradling Malia and petting her face. He tells Scott that this is where it all started and points to the safe where the Hales kept the bearer bonds. Kira looks around and picks up a jar of mushrooms. She asks how you change bearer bonds into cash. "At a bank, I guess. They just let it sit here the whole time collecting dust. You know bearer bonds are basically extinct?" "Why does it matter?" Kira asks. "You know how many problems that money could solve?" "For you?" "For me. My dad. The Eichen House and the MRI bills are crushing him." Scott explains that his mom adds up all their bills and all their income and calculates how long they have until she loses the house.
Outside, Lydia finds the Sheriff. She asks what's going on because her mom is inside the school. "We're working on it," he says.
In the vault, Scott can hear that people are looking for them. "Someone's going to have to go out there." The boys look at Kira and Malia. Scott says they need to tell Malia the truth about Peter. She's going to see the rest of the deadpool list eventually. "Try to remember that Peter's the one name missing on that list," Stiles says, "which either makes him incredibly lucky with a benefactor, she finds out about him, she's going to go to him, you know she is. And then he's going to twist his way into her head like he does everyone. Including us. We let him walk around like nothing ever happened. Like he's one of the good guys. Scott, he's not one of the good guys. If she finds out about him, she's gone. That's probably what he's waiting for, and if he wins, we lose." Scott tells him that they're already losing and shows him his bleeding hand.
At the hospital, 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 werewolves don't have long. "They're going to die without an antidote."
Stiles wakes Malia up and brushes her hair from her face. He tells her that he has to leave for a few minutes. He explains that whatever the illness is, it's worse for the supernaturals, which means it's another assassin. She grabs his knee, and he gives her his jacket to curl up in. "You're coming back, right?" she asks. He pets her cheek. "Yeah. Yeah, I'd never leave you behind," he replies, then kisses her on the forehead. She smiles and holds his hand, but he gets up and pulls away. They were able to open the vault door from the inside. It's unclear whether anyone can do that or if it still requires claws. It is also unclear if the vault can only be opened from the outside by Hale claws.
Derek is sitting at Braeden's bedside watching her sleep. She clears her throat, and he stands up so she won't catch him sitting so closely. She asks him what he's still doing there. "I'm protecting my investment," he replies, clearly a cover story. Melissa knocks on the door and lets Satomi in.
The Sheriff pulls Lydia aside and asks her if she has any kind of indication. "Is someone in there gonna die?" "Yes. And it's not just a feeling."
In the morgue, 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.
Stiles finds Natalie and asks her where Mr. Ken Yukimura is. She tells him that he's fine and is helping other students. As he's about to leave, Stiles realizes that Coach is the only adult who got sick. Natalie tells him to lie down, but he ignores her.
Derek asks Satomi who was shooting at the entrance to the woods. "Apparently another assassin. Personally, I'd rather face a gun than a variant of smallpox." Melissa replies, "Sounds like you're going to get plenty of chances." Satomi turns to look at Derek, and he catches her looking. "Sorry. I just noticed how much you remind me of Talia." Derek looks away, a few emotions flitting across his face. 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." Satomi didn't get infected because she'd been inoculated by the tea. Melissa perks up and asks how rare the mushroom is. "Can we find it?" "We don't have to. My mother kept some of it. It's in our vault."
Malia rolls onto her side and hugs herself. She reaches into the pocket of Stiles's coat and finds the deadpool list. Scott sees what she's doing and tries to stop her, but he can't get there fast enough. It doesn't end up mattering because she can't see.
Stiles rifles through Coach's office looking for something that could have infected him. He takes a second and looks at the papers on Coach's desk. They are stamped with Approved. As Stiles sifts through them, the color of the ink changes. Then he checks Coach's mug and sees black fingerprints there, too. He recalls the students having to sign in with their fingerprint at the PSAT and makes the connection. Simon catches Stiles in Coach's office. "I was wondering how that idiot got sick," he says. Stiles drops the mug. Simon asks where Stiles's friends are since in order to get paid by the Benefactor he has to have proof of death. He screws a silencer onto his pistol and then points it at Stiles. Coach coughs and suddenly comes to consciousness basically better. The non-supernatural kids all get better at around the same time. Natalie notes that Sydney's lesions are gone, and Sydney asks if she can take the test again now. Malia, Kira, and Scott are unable to see.
Simon pushes Stiles out into the boys locker room. He explains that the virus doesn't kill humans. "So don't you think you should tell me where they are? Shouldn't one of you get to live?" Stiles tells him that he saw them in the library. Or maybe the cafeteria. Simon lifts the gun. "I'm going to count to three, and then I'm going to kill you." Stiles turns around and faces the gun. "Think you can scare me?" "No, I think I can kill you. I just thought the countdown would make it more exciting." He holds the gun to Stiles's forehead and starts to count.
Stiles closes his eyes when Simon gets to two and starts to cry. A shot goes off, and Stiles's face is sprayed with blood. He sputters and looks up to see Agent McCall coming into the room. He shot Simon in the head from behind (and somehow the bullet didn't also go through Stiles). "Where the hell did you come from?" Stiles demands. McCall replies that he got a call from Melissa. "I don't know what it means. She said there's an antidote. It's in the vault, reishi mushrooms." The mushrooms are in a jar on one of the shelves. Stiles runs to tell Scott.
Derek tells Satomi that he has to get to the school. As they leave the morgue, a new, nameless assassin in a red coat appears in the elevator. She fires at Satomi, and Derek jumps in the way. Satomi didn't need the assist. She dodges the bullets and uses her piercer to stab the girl through the neck. She turns to the others as they come out to see what's happening. "I may have learned to control my anger, but I still know when to use it."
Stiles hollers through the vault door to Scott that the cure is in there with him. Stiles beats on the door, shouting Scott's name. "It's in there with you. It's in a jar. On one of the shelves." He shouts until he's hoarse and eventually sags to the floor. Scott is on the floor on the other side of the door, not moving. "Reishi. Scott, I saw it," Kira says. Scott pushes himself up and staggers toward the shelves. He uses his alpha vision to see and pulls himself up the shelf. He manages to knock the jar over, and the dust from it shattering is enough to spread the cure. Scott opens the door, and Stiles pats him on the back of the neck.
The Sheriff rushes into the school as the students all come out. Lydia finds her mother and gives her a big hug. Natalie apologizes. "I was just trying to get a little overtime."
Malia has seen the deadpool list. Stiles kneels next to her to ask her if she's all right, but she doesn't look at him. He touches her shoulder, but she grabs his wrist and pushes him away. She leaves without saying anything, and Stiles finally sees the deadpool list on the ground. He realizes what's happened and crumples the paper in his hand.