Rafael McCall oversees the transfer of William Barrow, the shrapnel bomber, to Beacon Hills Memorial Hospital. Melissa is just decorating for Halloween when she sees both her ex-husband and Sheriff Stilinski come into the ER. She can see the confrontation happening before it happens. The Sheriff tells Agent McCall that Barrow is not coming in, but McCall replies that this is the only hospital that he can go to. The county hospital punted him to Beacon Hills. Barrow is wheeled in, and Melissa looks upset because she's going to have to do the pre-op interview.
That same night, Stiles sneaks into the school to set up a Mischief Night prank for Coach Finstock. Stiles calls Scott and tells him that they have a job to do, so he needs to get down to the school. Scott claims to already be in bed and asks if they aren't getting a little old for pulling pranks. Stiles retorts that they do this for Coach. "I thought we did this to Coach," Scott replies. Stiles insists that Finstock loves this stuff. Mischief Night is also Coach's birthday. Stiles gets a screwdriver out of his locker as he talks to Scott. He threatens him and starts to count down, but Scott surprises him by already being in the locker room.
Agent McCall advises Melissa to be careful. Barrow is a former electrical engineer who decided to go onto a school bus with a shrapnel bomb. He killed four students and left another with no legs. Melissa asks if the psychiatrists have made any progress, and McCall tells her that all Barrow says is that he's going to do it again and get it right. Melissa begins the pre-op interview. She asks if he understands that scar tissue has formed around a piece of shrapnel still lodged in his body and that it is now blocking vital functions. She says they have to put him under general anesthesia tomorrow morning to perform the surgery to remove it. Barrow asks her if kids still pull pranks the day before Halloween. He tells her that where he's from, this night was called Hell Night. She asks if he has any allergies to any medications. He does not. She asks if he's taking anything other than temazepam and divalproex. He replies that he just takes what they give him. Mellisa tells the guards that she's going to need to listen to Barrow's heart. She opens his shirt, revealing a heavily scarred chest, and listens to his heart and breathing. Barrow leans up and tells her to ask what she really wants to know. She asks him why he did it, and he tells her that the kids had glowing eyes. Barrow jerks and starts to rant at her that their eyes were glowing, and Melissa makes her escape.
Monday morning, Scott arrives at school and sees Ethan and Aiden waiting for him. Aiden's the one in the blue shirt. The twins say they're not back at school, they just want to talk. Stiles comes up and says that must be a change of pace for them, since usually they're just hurting, maiming, and killing. Ethan says that Scott needs a pack and they need an alpha. Stiles isn't having any of that. Ethan argues that they helped when Scott couldn't roar. Stiles points out that all they did was beat the crap out of Scott, which really doesn't qualify as helping. Scott asks why he would say yes to them. "We'd make you more powerful. There's no reason to say no." Stiles almost rolls his eyes out of his head. Isaac joins the conversation and points out, "I could think of one. Like the two of you holding Derek's claws while Kali impaled Boyd." Isaac is totally up for fighting the twins right now, but Scott stops him. Scott refuses to let them into the pack because none of them trust them. Scott, Isaac, and Stiles walk away. Ethan asks what they're going to do now, and Aiden just looks at the Beacon Hills High School sign. Ethan's incredulous that Aiden actually wants to finish high school. He asks if it's about Lydia. Aiden replies that it's about proving to Scott that they should be in his pack. Aiden doesn't want to be an omega. He's worried about what will happen to them when all the people they've hurt find out that they don't have a pack to protect them. "We're dead on our own." "Dead's still better than being back in high school." Ethan says he's not going back, but then he sees Aiden staring at something over his shoulder. He turns to see Danny talking to another boy. Jealousy changes Ethan's mind, but only if Aiden will take math class for him.
Scott and Stiles head into school, and Stiles immediately gets hit in the face with a roll of toilet paper. He tells Scott that he made a good alpha decision about the twins. They stop at Stiles's locker, and Scott starts looking at Kira across the hall. Stiles notices and asks if he likes her. He encourages Scott to ask her out. "Scott, I don't think you get it yet. You're an alpha, okay, you are the apex predator. Everyone wants you, you know? You're the hot girl that every guy wants." Scott smiles at the thought of being the hot girl, and Stiles assures him that he's the hottest girl. Isaac has no idea what's going on but assures Scott that he is indeed the hottest girl, which makes Scott smile even more.
Coach Finstock cautiously opens the door to his office. He waves his hand near the ceiling to try to set off any traps. He flips on the light and jumps back, waiting for something to happen. There's a small wrapped present on his deck, and he pokes it with a stick to check if it's safe. Eventually, he lifts the top of the box and finds that it's full of screws and nails. He laughs. "That's all you got? That's it?" He lifts the box, and everything that's hanging on the walls falls down. The screws have also been removed from his chair and desk, so everything collapses.
Scott and Stiles are waiting in Business class. They hear Coach holler "Son of a bitch!" and come storming out and look very proud of themselves. Coach says they're all evil. Every Halloween his house gets egged. "A man's house is supposed to be his castle. Mine's a frickin' omelet!" He picks up another present on his desk in the classroom and smashes it without opening it. It was a mug with #1 Coach on it and a picture of him, apparently a present from Greenberg. Lydia is checking her phone during class and hears buzzing. She waves her hand around her head trying to bat a fly away. Danny notices and asks what she's doing, because he can't see any flies. The buzzing sound gets louder and louder.
The sound becomes the sound of the lights in the operating room where Barrow is prepped for surgery. The surgeon jokes about making a minor slip and letting Barrow die. No one else seems to find it funny. Once they get him open, they find what looks like a tumor instead of shrapnel. The surgeon asks for a 10 blade, but the nurse can't find it. Melissa tells the doctor to look, because the thing inside Barrow is pulsing. It bursts open, and live flies start swarming everywhere. Barrow sits up and slashes the surgeon with the scalpel. As the nurses come out of the room screaming, Agent McCall and Sheriff Stilinski rush in. A nurse is on the floor trying to keep the surgeon from dying, but Barrow is gone.
Derek and Peter have returned to Derek's loft. Derek sews Peter's severed finger back on. "Don't you have any anesthetic?" Peter asks. "Yep," Derek replies. Peter then asks what's in the triskele urn. Derek finishes the sewing and then opens the box. It contains five of Talia's claws, which he dug out of the ashes of the fire. "I can't decide if that's touching or morbid," Peter says as he holds up a claw. Peter asks what he's going to do with them, and Derek says he has to ask her something. He places the box in front of Peter, and Peter realizes that it has fingerholes built into it. He looks at his own hand. "You gotta be kidding." "Why do you think I sewed your finger back on?"
Melissa asks the Sheriff to talk. She tells him that the flies came out of Barrow's tumor, which pretty much isn't possible. But more, she tells him what Barrow had to say about the glowing eyes. Agent McCall tells everyone that stolen ambulance has been spotted at Truman and Spalding, which is three blocks from the school. The police all head out.
Aiden goes to see Lydia at her locker. She tells him no. He cannot show up with his cute little smile, the dark eyes, the brooding forehead, the muscles and suddenly they're ripping each other's clothes off in Coach's office. He just keeps smiling at her, and they do try to go to Coach's office. The desk has fallen over, though, so they leave to try the guidance counselor's office. They don't notice that Barrow was hidden behind the door. Barrow picks up a staple gun and uses it to close his wound.
Stiles chases after his father as they march through the school asking if the shrapnel bomber was really spotted nearby. The Sheriff tells him that it was a little closer than nearby. Agent McCall asks how they get down to the basement. He wants to make sure they have all the exits covered. Stiles asks his father what's really going on. "Barrow went after kids with glowing eyes, he said those exact words?" Isaac asks Stiles. Stiles explains about the surgery gone wrong as he, Isaac, Lydia, and Allison look for Scott. When he mentions the live flies, Lydia stops dead. Allison turns to her to ask what's wrong. Lydia says that all day she's been hearing buzzing.
Kira sits in her dad's classroom with him eating lunch instead of going to the cafeteria. She takes a photo of him with her phone and then one of the quote on the board, "History will be kind to me for I intend to write it. -Winston Churchill." He tells her that she should be embarrassed to be seen with him not keeping him company. He asks how she's doing with making friends. She says she doesn't know what her problem is, but every time she opens her mouth she just starts rambling. "Try again. Fail again. Fail better," Ken says. She asks if he's quoting Samuel Beckett, and he claims to think he was quoting Yoda. He assures her that someone will show an interest in her because she's beautiful. Scott approaches the classroom and listens from outside as Kira says she doesn't need a boyfriend, just friends. Scott looks a little sad at this.
Stiles runs down the hallway, finally finding Scott. Lydia reports to them that the police are leaving and asks Stiles why. He says that they must have cleared the building and grounds, so they don't think Barrow is at the school. Lydia is sure that he is because the buzzing keeps getting louder. Stiles chases after his father as they leave the school. He tells him that he can't go because Lydia knows Barrow is still around. The Sheriff asks if she's seen him, and Stiles has to tell him that she just has a feeling. "A supernatural feeling." "Lydia wasn't on the chessboard." "She is now." "Kanima?" "Banshee." The Sheriff rolls his eyes. "God. Really?" The Sheriff has to go anyway, though, because an actual sighting is more than he can ignore. He says they're leaving a few deputies on site and locking the school down until 3pm. "That is the best I can give you, Stiles." "Leaving me here? That is not the b-- that is the worst!"
Melissa McCall shows up at the school with some of Barrow's clothes. She gives them to Scott, who meets up with Isaac, Ethan, and Aiden so they can try to track Barrow through scent. Meanwhile, Allison breaks out of the school so she can start looking through the bestiary. She reminds Stiles and Lydia that it is literally a thousand pages long. Lydia reminds her that the word she's looking for is musca, which is latin for fly. Allison climbs out through a window, and Stiles and Lydia head upstairs to start looking. It's about 2:30.
In the basement, Isaac asks if they're really going to trust Ethan and Aiden. Scott says that asking for their help doesn't mean trusting them. Isaac tells him that he'd really like to see the twins dead, and Scott replies that Barrow might take care of that for them. Isaac smirks. Ethan and Aiden head down another hallway in the basement. Ethan thinks he hears something, and when they round the corner, they find Danny kissing the boy he was talking to earlier. Ethan is distressed. Aiden thinks it's funny. Danny acts a little ashamed.
Lydia and Stiles look through the art room. Lydia confirms that all the Werewolf are in the basement, in the boiler room to be precise. She stops to look at an image of an atomic bomb mushroom cloud, and they realize that an engineer could rig the boiler room to explode. Stiles decides that they have to get everyone out of the school, so he pulls the fire alarm. The Werewolf all leave at the sound of the alarm. Stiles looks pretty pleased with himself until Lydia looks at him, distressed. Finstock is standing right next to him, glaring. He hauls Stiles out of the building by his ear, yelling at him for pulling a prank when there's someone legitimately dangerous around. "If I were four years younger, I'd punch you!" Stiles doesn't get what the four years has to do with anything.
They catch up with the Werewolves, who say they didn't even catch a scent. It's 3 o'clock, so school is over. Stiles figures that if Barrow was going to set off a bomb, he would have already. Ethan asks if that means everyone's safe. Lydia replies that she doesn't know.
Coach Finstock finds Kira in the library, reading and listening to loud music. She didn't hear the alarm. He tells her to get the hell out of there. Barrow was in the library just a stack away.
Back at the loft, Derek drops Talia's claws into the holes of the urn. Peter looks incredibly doubtful about all of this. "You know there always an element of danger to rituals like this. I'm not particularly fond of them... unless they somehow benefit me." Derek grins and asks him what he wants. Peter claims he wants to keep the claws for sentimental value, which Derek does not buy for a second. Peter lets his hand hover over the urn for a few seconds, hesitant to actually do this. But Derek loses his patience and jams Peter's fingers down onto the claws. Peter's eyes flash blue.
Ken Yukimura arrives home and tells Kira to change into something nice for dinner because they're having a guest. He invited Scott over to thank him for saving Kira's life and to maybe get his daughter a boyfriend. At dinner, Mrs. Yukimura assumes that Scott's eaten sushi before at some pretty impressive restaurants but assures him that her husband is an excellent cook. Ken sets down a sushi plate. It has hamachi (yellowtail), uni (sea urchin roe), ikura (salmon roe), hirame (sole). It quickly becomes apparent that Scott's never had sushi before. Kira is embarrassed and complains that they were supposed to have lasagna. Ken wanted to impress Scott, and Scott is willing to try it. Kira shows him how to hold chopsticks. Scott tries to eat a piece but drops it. Kira catches it with her chopsticks and feeds it to him.
In Stiles's room, Lydia lies on the bed and watches Stiles add photos and strings to his wall. She asks him what the different colored strings mean. He says that green means solved, yellow's to be determined, and blue's just pretty. Red means unsolved. "You only have red on the board." "Yes, I'm aware, thank you." Lydia sighs and asks Stiles if he got detention for pulling the alarm. He tells her that he has it all week but it's okay because they were on to something. Lydia wraps a red string around her finger and expresses doubt that they were onto anything because they found no proof. Stiles can hear that she's upset at being wrong, so he tells her that she's been right every time something has happened. "No scent. No bomb. I got you in trouble." He unwinds the string from her finger. Stiles believes in her and tells her that if she wanted to he would head back to the school right then to keep looking for proof. Stiles uncaps the marker he's been playing with and has an idea about how Barrow could have not had a scent. He tells Lydia they're going to the school.
Allison sits in her dad's office reading through the bestiary. She hears a thumping outside and stands up, ready to fight if necessary. There's zapping and loud yelping, and she smiles a little. Isaac appears in the doorway. "Electrified the windows?" "Yep." "Didn't wanna... say anything about it?" "Nope." He heads in and offers to help, by which he means look at pictures since he can't read Latin. He hits a key on the keyboard, and the imagine of a red demon mask comes up. They both stare at it.
Peter has Talia's claws impaled on his fingertips. He tells Derek that this is going to hurt a lot. "Just do it." "Oh, I'm going to. I just wanted you to know. We all have our petty revenges." He jabs the claws into the back of Derek's neck.
At dinner, Scott asks the Yukimuras about their family. They moved in from New York, although Mrs. Yukimura has several generations of family ties to Beacon Hills. Mrs. Yukimura is Japanese, but Ken is Korean. He took his wife's name when they got married because she was the only surviving member of her family. In Japan, a married couple must have the same name so they can belong to the same koseki. Ken says his wife's ancestry is pretty unique and he was going to discuss it in class, but Kira asks him not to. While they talk about Mrs. Yukimura's heritage, Scott looks like he's choking. Kira asks him what happened to his wasabi, and he says he thought it was guacamole.
Stiles and Lydia head into the chemical storage closet, which is supposed to be locked. They deduce that Barrow used chemical scents to cover his own. Stiles then finds bloody staples on the floor, which confirms that Lydia was right. She doesn't feel good about the discovery, which Stiles think is probably because Barrow was there to kill someone. They go around the Chemistry lab looking for clues. Lydia spots numbers on the board: atomic numbers. Potassium, Iodine, and Radium. She writes out the symbol for each one, and it spells Kira.
Derek wakes up into a vision. The nemeton is growing out of the floor of the loft. He looks up, and a black wolf trots in. It stops on the nemeton and flashes red eyes at him.
Scott calls his mom and tells her proudly that he ate sushi. He asks her why she never changed her name back to Delgado, and she tells him that since Scott's last name was McCall she wanted to keep it. She has to go and hangs up. Kira comes in with some soda and a pizza. Scott is thrilled. They sit down on her bed and eat. Scott gives Kira a warm look.
Allison and Isaac go through her findings. She says flies can carry messages to the dead. Isaac says all he found was Beelzebub, the Lord of the Flies. They are sitting very close together, and Allison turns to look in Isaac's eyes. He leans in to kiss her, but she stops him. "Are you serious?" He plays dumb and claims he wasn't trying to kiss her, but then admits that maybe he was. Allison hops up off the bed and protests too much how she would never kiss another Werewolf. Isaac doesn't believe her and declares that he won't ever kiss her either. Then he takes off his shirt. Allison stares at him a second and then takes her own shirt off. Chris Argent walks in and the both of them quickly grab their clothes and put them back on. Chris tells Allison he wants to see her in his office. "Where I keep my guns." He shoots Isaac a look. "Another Werewolf!" Chris shouts as soon as Allison is out of the room.
Peter looks like he's having a seizure and pulls the claws out. He demands to know what Derek asked Talia and what she said about him. Derek turns and glares at him, which Peter interprets as a bad thing. Derek just pants.
As Scott leaves Kira's house, he thanks her for dinner. "The pizza was good." Kira tells Scott that he seems like a nice guy and not just because he kept her from being eaten by a coyote. He also remembered her name. They smile at each other. And then Barrow runs up behind Scott and knocks him out with a tire iron. Scott wakes up to Stiles and Lydia standing over him. Scott tells them that Barrow took Kira, but Stiles tells him that they already know. Scott calls Isaac to see what he's found, but they've only found information about flies and the dead. Scott says they need to think because Barrow's going to kill her. They ask Lydia what she hears now, but she says nothing. She tells them that she feels like she can do this, that there's something important on the tip of her tongue and it makes her want to scream. Stiles tells her to scream.
Lydia lets out a banshee wail that hurts even Stiles's ears. After she does, she hears buzzing again, but this time it sounds like electricity. Stiles says that Barrow worked at a power substation. Scott asks him which one.
At the substation, Barrow disconnects and electrical line with an ax. He has Kira tied up on the floor. She asks him what he's doing, and he says that right now he's going to take her picture. He grabs her phone from her pocket and snaps a few photos. He says he's making sure he has proof for all the people who never believed. Once he has his photos, Kira asks him to let her go. He just shakes his head and asks her if she's ever seen Village of the Damned, the original. " Not the remake. Nobody cares about crappy remakes." He explains that the movie is about a group of blond-haired beautiful children who can make their eyes glow. "And they do terrible, terrible things." Barrow rants that when he told everyone he saw children with glowing eyes no one believed him and wouldn't do anything. It was like they were paralyzed, but he's going to shake everyone out of their paralysis. "I am going to galvanize them."
Scott, Stiles, and Lydia arrive at the power station. Stiles tells Lydia to stay in the car because he only has one bat. Scott runs in and finds Kira. She calls his name, and then Barrow hits him with an electrical line. The shock sends Scott flying. Barrow approaches Kira with the sparking power line. Scott tries telling Barrow that Kira isn't the one he wants. Barrow touches the line to Kira, and her body glows. The substation explodes. Barrow appears to be dead. Kira absorbs all the electricity into her hands as Scott watches. All of Beacon Hills falls dark. The power in Allison's room goes out, and suddenly black figures in masks start circling Isaac. They attack him and slam the door. Chris and Allison rush for the door, pounding on it and demanding that he open it, but they cannot get in.