It's Mischief Night, and kids in the neighborhood go around smashed Jack O'Lanterns. They look up and see five shadowy figures marching up the street. It's the same creatures in masks that attacked Isaac. For lack of a better term, these Oni appear out of darkness and wear black masks.
Allison and Chris finally get through the door and find Isaac on the floor, freezing and shaking. Chris tells Isaac that he needs to shift to trigger his healing. He slaps him a few times in the face, then punches him. Isaac's eyes flash yellow, and he growls. He comes back to himself, crying, and scrambles away from them. He asks if they saw the five figures. Isaac says he could see the eyes of one of them, they were greenish yellow, like a firefly. Chris gets up and checks the window. The security system wasn't triggered. Allison asks how they got in, but Isaac says they came out of the shadows. Chris reacts to this information knowingly. Allison thinks he knows something, but he won't say what. He asks them to keep the attack quiet for 24 hours. Isaac clearly wants to tell Scott, and Allison isn't happy about keep this secret. She says they could have killed Isaac. "But they didn't. And I think there was a reason why. I think they might have been after me," Chris says. He goes into his study and gets a box. Inside are the broken pieces of one of the Oni's masks.
Down at the sheriff's station, Rafael McCall tries to get the story out of Stiles, Scott, Kira, and Lydia. He asks Stiles when they got to the power substation. Stiles replies that he got there at the same time as Scott. The boys try to confuse Agent McCall by questioning who he's directing his questions to. "I think he's asking both you," Lydia offers. Agent McCall tells them that he'll answer the questions, then corrects himself. Agent McCall reads back the series of events: Barrow was hiding in the chemistry closet at the school. Someone left him a coded message on the blackboard telling him to kill Kira. Then Barrow took Kira to the power substation and tied her up with the intent of electrocuting her, which blacked out the whole town. Stiles agrees that that sounds right. Agent McCall asks how they knew he'd take her to a power station. "Well, cause he was an electrical engineer. Where else would he take her?" "That's one hell of a deduction there Stiles." "Well, what can I say, I take after my pops. He's in law enforcement." Stiles winks and points at his father, who can't help but smirk. Agent McCall then asks Scott and Kira what they were doing. They alternately answer "eating sushi" and "eating pizza" until they both answer together "Eating sushi and pizza." Agent McCall asks Sheriff Stilinski if he believes any of this, and the Sheriff replies that he hasn't believed anything Stiles has said since he started talking. This is not the first time the Sheriff has said something like about his son. He adds that he thinks the kids found themselves at the right place at the right time and Kira is very lucky for it. McCall asks Kira if that's how she remembers it. Everyone looks at her expectantly, and she says yes. Kira then asks for her phone back. Unfortunately, because Barrow used it, it's evidence. He has an officer take her away and sign some paperwork. Agent McCall stops Scott as they leave the office and reminds him that if half the story about Barrow is true then not only did someone help set him loose, but he was just a pawn in a larger game. "A mass murderer is bad enough. A mass murderer being controlled by someone? Far worse." He sends Scott home because it's a school night.
At home, Kira lights some candles in front of her mirror. She takes a photo of herself with the flash on. The resulting image shows an orange, glowing aura swirling around her. She looks distraught but not surprised.
The next day, Coach walks around the hallways of the school with a megaphone, announcing that class starts in 5 minutes. "Just because there's no power, don't expect there to be no school!" Stiles comments on Coach's triple negative and then knocks his keys out of his locker. He picks them up and peers curiously at a key he doesn't recognize. "Hello, where'd you come from?" Scott comes into the school and immediately goes to talk to Kira. She turns away and goes to her locker instead. Stiles stops Scott and tells him that until they know if she's a psychotic monster, he votes against any and all interaction. "What if she's like me?" "That girl walked through 1.21 jigawatts of electricity. She's not like you." Scott walks away, and Stiles gives the key another concerned look.
In the boys locker room, Danny is on the phone with a party venue. He asks them if they have generators or something. He's trying to throw a blacklight party, so it's not like they need a ton of power to pull it off. The venue says no, and Danny hangs up, frustrated. Ethan overhears the conversation and offers to help Danny find a new place. "What's the point? Nothing in town's going to have power." Danny walks away, and Aiden comes up to his brother. "You want to throw a Halloween party? What's next, we gonna join the Yearbook Club?" Ethan explains to his brother that he just wants to do something nice. "You don't get it, do you? Scott doesn't care about power. He cares about people. You wanna be a wolf in his pack? Try being a human in high school."
Aiden sits next to Lydia in Biology class. Mrs. Martin, Lydia's mom, is serving as a substitute since Mr. Harris took up a new occupation as a human sacrifice. She asks Lydia not to embarass her, and Lydia makes a comment about her shoes. They smile at each other. Lydia has brought a Physics book to her Biology class. (NOTE: Harris was last teaching Physics, so the Biology reference is an error.) Aiden asks Lydia why she's copping an attitude, since he's not the one who killed Mr. Harris. She doesn't answer at first. Then she says, "The other night, I helped save someone's life. That felt really good. And I look at you, and all I can think is that you helped kill Boyd. You're not just a bad boy, Aiden, you're a bad guy. And I don't want to be with the bad guys." Aiden then turns around and tells Danny that he thinks he knows a place where he can have his party. Derek is at his loft. He grabs his coat and heads out.
Kira sits in the hallway by herself eating lunch. Scott sits down next to her. She tells him that she doesn't want to walk about it. He offers to talk about the Pre-Calc test on Friday instead. Kira decides to show him her secret. She tells him to take a picture of her with the flash on. He sees the same orange aura. She does know what it is, just that it showed up a few months ago. It only shows up when the flash is on, and she doesn't know how Barrow knew about it. "He used my own phone to take pictures of me," she says. Scott realizes that this is why she wanted to get her phone back, so no one would see the photos.
That night, Derek returns from his errands. He went out to buy candy for trick-or-treaters! Some kids come up to him in the parking lot asking for candy. Derek stares at them all and reaches slowly into the truck to get the bag of candy. He hands out the M&Ms silently, and the kids all continue to stare at him. Derek flashes his eyes and fangs and snarls at them. The kids run away, and he smirks to himself. Derek drops the candy back in the truck, and then the Oni manifest in a circle around him.
Up in the loft, Danny checks the place out. He asks Ethan where the guy who lives there is. "He's out of town." Aiden is outside starting the generator. Ethan flips on the blacklights, and Danny smiles.
Scott and Kira meet Stiles at the sheriff's station. Stiles hands them a stack of keycards, one for the perimeter doors, one to the evidence room, and one to the Sheriff's office. They ask Stiles if he stole them all, and he replies that he cloned them with an RFID emulator. "Is that worse than stealing?" Scott asks. "Smarter," Stiles replies. Kira pulls Scott aside to ask him something, and Stiles is slightly offended that he's not being included. She asks what Scott told Stiles about the pictures, and Scott says that he told Stiles the phone had naked photos on it. Kira doesn't seem sure if that's better or worse than the truth. When they come back, Stiles continues explaining that almost all the police are out dealing with the blackout but there will be someone at the front desk. He tells them to go in by the service door by the Dumpster. Stiles promises to text them if anyone comes out of the station, but if they get caught, he can't help them. His dad is under investigation for impeachment, so if anything happens he'll run and leave them both for dead. Scott and Kira hurry inside. They hide behind desks to escape the one officer who walks through, then go into the evidence room. Kira finds her phone, but the battery is dead. Kira wants to take the phone, but Scott says they'll notice that too easily. She asks how they can charge it with the power out, and Scott spots his dad's laptop on the desk nearby. When he opens the laptop, Scott is momentarily thrown to see that his dad's wallpaper is a picture of Scott as a baby. They plug the phone into the laptop and let it charge.
Outside, Stiles sees Agent McCall pull up. Despite his earlier warning that he'd leave them for dead, Stiles decides to get involved. He runs into the sheriff's station and interrupts Agent McCall before he can get back to the evidence room. Stiles tells him that he was thinking about the case and he thought that maybe he should share his thoughts. Stiles says that since Barrow received the information about who to kill at the school, that maybe the accomplice works at the school. Kira's phone gets enough power to turn on. Agent McCall informs him that they've already thought of that and started looking for links between Barrow, faculty, and students last night. In fact, Sheriff Stilinski thought of it. "His one useful suggestion." McCall goes to enter the evidence room again, but Stiles stops him. "Hey, you know, this attitude that you have towards my dad, you can dress it up to all the professional disapproval that you want, but I know the real reason you don't like him." McCall smirks. "Is that so?" "Yeah, because he knows something that you don't want him to know. And guess what? I know it too." Stiles stares Agent McCall down, and McCall tells him to go home. Scott and Kira escape the evidence room before Agent McCall enters. Stiles walks away and meets them outside. Kira is thrilled with what they've just done. She asks them if they've ever done anything like that before. "Yeah, once or twice," Stiles admits. Scott offers to take Kira home, then asks her if she wants to go to a party instead.
Isaac and Allison arrive at the loft. Everyone is painted and dancing. "Derek can never know about this," Isaac says as they look at everyone. Allison looks stunned. Ethan asks Danny if he's happy with how it turned out. Ethan has glowing claw slashes painted on his chest. He tells the artist that Danny needs to get painted. She asks face or body, and Ethan rips Danny's shirt off. Someone calls out for more ice, and Ethan goes to handle it. While Danny is getting painted, the Oni show up. He seems to notice that something is wrong, but they don't come after him.
Ethan goes into a back room to get some bags of ice. The light bulb does out, so he fiddles with it to turn it back on. It goes out again, and then the Oni appear. When the light goes out a third time, they attack.
Stiles, Scott, and Kira arrive at the party. Stiles tells Scott about the mysterious key. He asked his father about it, but he didn't put the key there. "It's just a key, right?" Scott asks. "Yeah, but it's not mine. And I don't know how it got there or what it's for." Scott asks if Stiles wants to leave the party to figure it out. Caitlin then comes up and kisses Stiles on the cheek, and he decides to stay. He follows Caitlin into the crowd. Scott notices Kira being uncomfortable in the crowd and takes her hand so they don't get separated. She thanks him and smiles a lot. Scott smiles too, until he sees Allison. He can't stop staring at her, and Kira lets go of his hand. Scott loses Kira in the crowd, so he uses his alpha vision to look for her. He learns that he can see her aura this way, and it looks like a golden fox. Stiles catches up with Caitlin. She doesn't recognize him from when they met before in the hospital. Stiles asks her how she's doing with the fact that her girlfriend died. She says that she's okay and really drunk and then asks him if he wants to dance.
Lydia is by herself. Aiden sneaks up on her and growls with glowy red fake teeth. "Not as good as the real ones," he says. "Or as lethal," she replies. "Okay, sure, I deserve that. I deserve basically everything you say. But, you know, I was pretty instrumental in setting all this up." Lydia is not impressed. She tells him that if she wanted to go to a rave she'd get into a time machine and go back to the 90s. She taps him on the arm and walks away. Aiden growls and shows his fangs in frustration.
Allison and Isaac stand next to each other off the dance floor. Isaac asks her if she told Scott what happened. "No, we still have a couple of hours, remember? We promised my dad." "You promised your dad," Isaac clarifies. He says he doesn't like keeping secrets from Scott, and he doesn't just mean the Oni. Allison says they're just standing there awkwardly waiting for someone to notice them and then Isaac likes to make things incredibly uncomfortable. Isaac thinks Allison is mad. "I'm not mad." "No?" "No." "Okay." "I'm frustrated." "Sexually?" She just looks at him and laughs. Allison heads over to the glow paint station. "Do you want to talk about Scott or do you want to paint my body?" she asks Isaac. He votes for painting her body.
Lydia watches Allison and Isaac dance together. "Ugh, finally." She spots Stiles dancing weirdly and calls him awkard. And then she sees Aiden grinding with two girls and calls him predictable. She suddenly senses that something is wrong and looks around. She starts calling for Scott, but he doesn't hear her. Lydia rushes outside onto the balcony to catch her breath. The Oni appear around her. She tries to scream, but the leader silences her.
Danny bumps into Aiden and calls him Ethan. Aiden corrects him, and Danny asks where Ethan is. No one's seen him for half an hour. Aiden looks worried and heads off to find his brother. Danny follows him.
Caitlin brings Stiles a beer and asks if he has a bottle opener. She takes his keys from his hand and points out that his key as phosphors on it. They both look at the key closely, and then Caitlin leans up and kisses him. Stiles is surprised because he thought she liked girls. "I do like girls. Do you?" "Absolutely." "Great." "So you also like boys?" "Absolutely. Do you?" Stiles doesn't answer her, but he gets an expression on his face that looks like revelation. Caitlin smiles and kisses him again. Stiles breaks off the kiss to ask her what phosphors are. She explains that they are a substance that luminesces. They're found in laundry detergent and in the paint they're wearing. They kiss again, but Stiles stops suddenly. He asks how he'd get phosphors on his key, and she asks if he's been handling chemicals. Stiles suddenly realizes that he knows where there are chemicals. He gets up, apologizing profusely. He runs away, then comes back and gives her a bottle of water telling her to drink the whole thing, then leaves again.
Scott and Kira escape to the roof. She tells him that he has paint on his face, and when he can't get it off, she licks her thumb and wipes it away. Scott starts to laugh because she "mom'ed" him. She asks him how he's okay with her freakish photo. She thinks her photo looks like a demon, but Scott tells her it looks like fox armor protecting her.
Isaac and Allison hold hands and dance closer. They're about to kiss when Allison notices something behind Isaac's ear. She pulls him to the storage room to get a better look. It's reversed number 5. They find Ethan on the floor, shaking like Isaac had been when the Oni attacked him. Danny finds Lydia outside in a similar state. They bring her inside and put her near a heating vent. Aiden wraps himself around her, while Danny looks for a blanket. Isaac breaks Ethan's arm to trigger his healing. They find the same reversed 5 symbol on Ethan and Lydia.
Outside, Derek wakes up next to his truck in the parking lot. He has the same mark. He howls, and Scott hears him. It's the first Scott knows of Derek being back. Derek goes up to the loft and approaches the DJ. A bouncer stops him, telling him that Bloody Beetroots doesn't take requests. Derek tries a second time, and when the bouncer stops him, he grabs him by the throat and throws him aside. Derek throws the DJ's table to the floor and roars for everyone to get out. They all flee.
Aiden tells Danny to get Lydia out of there. Lydia protests that she has to find Scott. Isaac, Allison, and Ethan arrive. Then Scott and Kira. The Oni are standing in the room waiting. They all turn to face Aiden. "Guys. They're all looking at me. Why are they all looking at me?" Scott and Derek both decide to attack. Derek manages to break one's neck, but it is unaffected and responds by throwing him into a pillar. Another one knocks Scott down. Isaac runs forward to try his luck, whipping out his claws, but the Oni draws a sword out of its chest, and he backs down. The Oni take Aiden and give him the mark. Scott gets up and places himself between the Oni leader and Kira. She can see his fangs and glowing eyes. The sun comes up and shines through the loft windows, wiping the Oni away. "What the hell were those things?" Scott asks. Isaac tells Allison that her dad's 24 hours are up.
Chris Argent stumbles back to his apartment, bloody. His phone rings with a call from Allison, but he doesn't have the strength to answer. He collapses in the hallway.
Stiles goes to the school and straight to the chemical storage closet. The key he has opens the lock, and the realization that he's behind this starts to dawn. He then goes to the blackboard where the atomic numbers were written. Stiles picks up the chalk and writes the numbers. The handwriting is a match.