At the Animal Clinic, Scott is assisting Dr. Deaton by holding down a dog for an injection while its owner frets over the procedure.
The dog’s name is Bullet. His owner explains that all of his dogs have gun-related names because he is from a military family.
As Scott pets him, Bullet rolls over and presents his belly in a sign of submission. This prompts his owner to say “Looks like he knows who the Alpha is.” This alarms Scott and seems to disturb Deaton.
Outside, Bullet’s owner attempts unsuccessfully to get the dog into his silver Toyota Corolla. Instead the pup runs off between two warehouses. The owner follows and believes he has found the dog under a dumpster. When he reaches in, he gets bitten and blood wells on his hand. He then sees Bullet is sitting across the way. When he again looks under the dumpster a voice whispers “Closer, come closer”.
Scott discovers a single mistletoe berry while sifting through a sample of Bullet’s stool. Deaton explains that the plant is poisonous to dogs and humans. Scott hears Bullet barking outside and goes to investigate. He finds the dog but the owner is no longer there.
At school, Ms. Blake finds Derek waiting in her classroom. She picks up a wooden pointer and wields is awkwardly as a defense. She fears he is there to intimidate or kill her to keep her silent about the events of Fireflies. She reveals that her name is Jennifer and that she has been in psychotherapy. She and Derek discuss “The Crucible” - a Play by Arthur Miller. Derek explains that it’s an allegory for McCarthyism. She promises to never tell about what she's seen and seems nervous but intrigued by Derek.
Stiles is wondering if the latest missing guy, Bullet’s owner, was a virgin. Scott jokes that he's not because Deaton makes him have sex with all his clients. He says it’s a new policy at the Animal Clinic. Stiles gets upset pointing out that if the killer is after virgins that he is in danger and needs to have sex immediately.
They are in the locker room and are overheard by Danny who says he’ll do it and that Stiles should come by his house around 9pm and plan to stay the night because “I like to cuddle”. It’s a joke of course but Stiles believes it just long enough to feign hurt feelings when Danny laughs and walks off.
Isaac returns to school and Coach Bobby Finstock welcomes him and explains that participation on Cross Country team is mandatory for all lacrosse players because he doesn't want them to get fat in the off season. Nike apparently provides the school’s Cross Country uniforms and gear.
Outside a few minutes later, Isaac is lacing up his running shoes. The Alpha Twins, Ethan (in black) and Aiden (in burgundy), stalk up to him on either side. When the whistle blows, everyone starts running with the Alphas way out in front.
Scott tries to get him to wait but Isaac chases after them. He loses sight of them again until one pushes him off the trail and down an embankment. They subdue him and are about to beat him when Scott shows up and punches Ethan hard, breaking his jaw. All four wolf out and prepare for battle but are interrupted by a scream.
Running to find the source, they reach a group of students surrounding the body of Bullet’s owner. He has been killed in the same manner of the other three, throat cut, bludgeoned and strangled with his dog leash.
The Sheriff arrives and takes control of the scene. Scott reveals that the victim was a senior. A girl (the victim's girlfriend) arrives and starts crying.
Isaac is convinced that the Alpha Twins knew something about the murder. Stiles believes the killings don’t involve werewolves “a lack of werewolfitude”. Scott is caught in the middle but believes both sides make good points. Isaac says he’s convinced the Alphas are responsible and he plans to kill them.
Derek’s sister Cora is working out in his loft. She does pull-ups then drops to the floor doing push-ups. There is tension. Derek tells her to stop because she is not done healing. She refuses saying she plans to go after the Alphas. Derek kicks her hand out from under her and she tumbles to the floor. Cora is livid saying she came back to town because she heard about a powerful new Alpha, one of the Hales, and that she had been waiting for this kind of news for a long time. She apparently did not know Derek was still alive either.
An alarm sounds and Kali and Ennis show up and the four begin to fight. Ennis quickly subdues Cora and Kali beats Derek into submission before stabbing him through the lower back with a steal pipe.
Deucalion enters and begins explaining what he wants. Derek assumes he wants to kill him but Deucalion seems offended saying “Don’t throw me in with sociopaths like your uncle”. He says he is always on the lookout for new talent and wants Derek to join his pack. Derek says he wants him to kill his Betas but Deucalion corrects him saying he only wants him to kill one and then he’ll want to kill the rest.
Deucalion explains how he accidentally discovered that killing one of his Betas allowed him to absorb their power. Once he became blind, one of his Betas felt he was no longer able to lead so he tried to kill him and take control. Deucalion bested him, killed him, and found that he became faster and stronger because of it. He says Kali and Ennis have both killed their entire packs. Kali says it was liberating. Deucalion says Derek’s pack, a couple of maladjusted teenagers, are bound to become a liability.
Allison fell asleep in Ms. Morrell’s French class. As the teacher calls her name is French, Allison dreams it is her mother, Victoria Argent, shouting her name and snaps awake. Once the rest of the class is gone, Allison and the teacher face off about their encounter in Chaos Rising. Neither is willing to give the other information on the why of them being in the bank and Ms. Morrell assigns lunchtime detention to Allison for sleeping in class.
Mr. Harris is teaching Inertia vs. Momentum. Scott is trying to convince Isaac to wait to confront the Alpha twins but Isaac stands up quickly and asks to be excused to go to the bathroom. Harris consents but when Scott says he has to go too, Harris refuses saying that if Scott’s “bladder suddenly exploded and urine began to pour from every orifice” he still wouldn't let him go.
In the hallway, Isaac confronts the Twins but Aiden begins beating Ethan, slamming his head into the locker and then throwing him at Isaac’s feet. When Harris and the class spill into the hallway, Ethan blames his injuries on Isaac. Later at school, Scott and Isaac see Aiden flirting with Lydia who turns him down for a date.
Stiles confronts Ashley, the girlfriend of the latest victim. We learn his name was Kyle and Stiles wants to know if he was a virgin. She slaps him but says he was not a virgin. Then his dad yells at him for interfering pointing out that the FBI has come to town because they have a full blown serial killer on their hands.
At Derek's Loft, Deucalion seems to know about the twins targeting of Isaac at school. He tells Derek that one of his Betas is getting in trouble.
Lunch time detention finds Allison paired with Isaac she asks him not to mention that she was at the school during Fireflies. He is still angry about her stabbing him with knives. Allison corrects him that they were Chinese ring daggers. Allison apologizes.
They get locked into the janitor’s supply closet, a soda machine is shoved up against the outside of the door blocking even Isaac’s enhanced strength from freeing them. He begins to panic, flashing back to the chest freezer in which his father locked him up. He beats on the door; eventually he wolfs out and turns on Allison. At that moment the door flies open and Scott pulls Isaac outside. He roars his name and Isaac calms and begins to apologize. Allison has two bloody scratches on her arm.
Scott and Issac plot to get the Alpha Twins angry.
A makeshift memorial has been set up at Kyle’s locker. Boyd approaches and pins up an Air Force ROTC patch attached to a note card with “Crossed Into the Blue” written in sharpie. Stiles greets him and mentions that he didn’t know he was back at school. Boyd says they’re not friends so why would he bother telling him. Boyd explains that Kyle and he were in ROTC together. Stiles concludes that they must have been friends but Boyd says he only had one friend and “she’s dead”.
Stiles explains to Lydia that there is a temple in Calcutta, India where they once sacrificed a baby every day. Every day was dead baby day. She doesn’t get why he’s telling her about human sacrifices and he explains that Scott is dealing with the Alpha Twins. She doesn’t know about the Alpha Twins but pretends that she does.
Stiles lays out his theory pointing out that the sacrifices are coming in threes – three virgins then three of something else which would explain why Kyle was killed even though he wasn’t a virgin. Lydia points out that it’s impossible to discern a pattern from a single data point meaning they would need another victim before a pattern could be established.
Lydia says maybe it’s not Stiles job and maybe he should leave the investigation of this human crime to the human Sheriff.
Allison hotwires one of the twins’ MV Agusta motorbikes. She gives Isaac a quick lesson in how to ride it.
Scott arrives in Ms. Blake’s class and begins popping motorcycle parts out of his backpack in front of the twins. Out in the hall, Isaac speeds along on the stolen motorcycle. Aiden becomes enraged and rushes out into the hall, stops the speeding bike with his bare hands and demands that Isaac get off. Isaac does by flipping over Aiden and leaving the Alpha holding the bike as students and Ms. Blake rush out into the hall to see what was happening. The teacher says Aiden will be suspended.
Back at the loft, Deucalion touches Derek’s face and says that Kali was right, he looks like his mother.
Derek, steel pipe still imbedded in his torso, says Deucalion is a fanatic. The leader of the Alphas explains that Derek has never seen anything like him before. He then launches into the following speech accompanied by lightning and thunder from an approaching storm.
I am the Alpha of Alphas.
I am the apex of apex predators.
I am death, destroyer of worlds.
I am the Demon Wolf.
On the last line his voice rises in volume to the point that his dark glasses crack.
Kali removes the pipe and Derek collapses on the floor.
Lydia draws a tree with a pen; black and barren branches bend and twist across the page. Danny comes up and comments on how good her drawing is and says she should be in art class. Lydia seems distracted. Danny then points out that she is in the music classroom and we see that she is surrounded by students with various instruments. Danny holds a trumpet. Lydia clearly has no idea how she got there. Someone shouts “15 minutes”. Danny explains that they’ve waited for the teacher for 15 minutes and can now leave because he didn’t show up.
The class exits but Lydia is drawn to a Samsung Galaxy Note II that is propped up on the piano. She realizes that the device is still recording and hits playback. We hear the teacher playing and then a discordant note and the playing abruptly stops. Then Lydia hears chanting on the recording. It is the same chanting we the audience have heard during each of the previous murders.
Stiles goes to see Dr. Deaton saying that his father is handicapped in his investigation because he doesn’t know that supernatural stuff is going down all around him. He explains that he’s found everything about the murders so far seems to point to the Druids, an ancient religious class about which little is known but much is imagined and speculated.
He also draws comparisons to a real case of human sacrifice discovered in England called “Lindow Man” an ancient body discovered in 1984 in England with mistletoe pollen in his stomach and the same threefold injuries of the recent murders in Beacon Hills.
Stiles points out that Deaton seems to know a lot about what’s going on that he hasn’t yet told Scott and his friends.
Deaton explains that he’s spent every moment of the past 10 years trying to push something away and that denying it and lying about it has become a pretty powerful habit. Deaton then explains that the killer is NOT a Druid but is simply copying the centuries old practices of a people who should have known better.
He then explains that the word “Druid” in Gaelic means “Wise Oak” saying they were close to nature and were philosophers not serial killers. Stiles gets a call from Lydia who tells him the music teacher has been taken.
Deaton and Stiles join her at the school. They listen to the chanting and Deaton asks for a copy so Lydia makes one and uploads it to Dropbox. He explains to Stiles that each grouping of three would have its own purpose – he lists virgins, healers, philosophers and warriors. Stiles stops him there having found a picture of the music teacher in military uniform and remembering that Kyle was in Junior ROTC. They immediately think of Boyd since he too is in ROTC but then Lydia remembers that Mr. Harris has a military connection as well.
In his classroom, Mr. Harris is grading papers when chanting begins.
In the school hallway, Isaac and Scott are confronted by Ethan and Aidan who strip down and merge into one large Alpha. They run from the giant but he easily catches them and tosses them down the hallway. Deucalion enters and the boys demerge and look shamefaced. He then removes the cap from his cane revealing a small knife in the handle. He sweeps it quickly at the twins cutting both on the cheek in one swipe.
In Harris’ classroom, Deaton, Lydia and Stiles search for clues. They find a test graded with an “R” and another graded with an “H”. They put all the tests together and it spells out the word – DARACH (Dah-Rahk) which Deaton explains means “Dark Oak”. That was how the Druids described one who “went down the wrong path”.
Derek tells Isaac he has to move out of the loft. He makes excuses, claiming having both Cora and he under the same roof is just too much. When Isaac protests, Derek throws a glass at him that shatters on a wooden beam column near Isaac’s face. Near tears, Isaac does as Derek commands while Cora listens out of site. Isaac goes to Scott’s house.
In the pouring rain, Adrian Harris is tied to a tree. He begs for his life, telling the killer that he “did what you asked. I did everything. They’re going to figure this out and they’re going to find you. You still need me.” With that, the killer twists the stick, tightening the garrote around Harris neck, apparently killing him.