While the teenage boy stumbles around, Peter makes his move and attacks Scott, biting him. Once he's finished, he lets Scott go, the frightened teenager running away from the werewolf as fast as he can. Peter now intends to bring his new beta into his pack.
When Scott suffers the symptoms from Peter's bite over the next couple of days, Peter keeps an eye on him. One morning, when Scott wakes up in the forest after sleepwalking into the forest the middle of the night, he spots Peter nearby. The fully transformed werewolf lures his progeny into chasing Peter, but Scott soon loses him.
Peter appears during the night, and tracks down the bus driver for the school, Garrison Meyers. Peter was looking for Meyers because the bus driver was once a former insurance investigator who was assigned to the Hale fire and had covered up the arson as an accident+.
Peter spies on Scott and Derek, listening to them as the latter is telling Scott a fully transformed alpha is committing the murders and responsible for biting him.
Peter is seen when Argent hunter Kate Argent comes to town. He stalks, and follows the hunter in her car with enhanced speed. Once she puts on the breaks, Peter attacks. He leaps on top of the roof of the car. He tries to grab her through the window but Kate reacts quickly managing to shoot the werewolf with a shotgun, wounding him, but he escapes. Derek is tracking him, and he comes across the blood. The alpha picks up on Derek taking chase. However, Derek is prevented from following when he gets shot by Kate instead.
Derek and Scott were unaware the older werewolf is actually fully conscious. They were unable to pick up that Peter's werewolf status and his face was only burned because Peter was both hiding his scent and consciously disabling his healing factor.
The store clerk was an ex-convict for arson who'd participated in setting the Hale House aflame, and Peter again kills in vengeance+.
Peter notices Jackson Whittemore is also in the store after the teenager catches a glimpse of him. Jackson is eventually pinned beneath the werewolf. Peter notices the claw marks on the nape of Jackson's neck. The alpha reconsiders killing him, touching the terrified boy's neck. The marks are spiked with nordic blue monkshood, a rare form of wolfsbane, which glows in response to Peter's touch. Peter leaves Jackson alive. He makes his escape, crashing out of the store's front window.
Peter follows Scott to the Argents' residence, stalking his werewolf progeny, where he listens to Scott's romantic rendezvous with Allison Argent. When Scott leaves, Peter ambushes him when he goes out to his car. Scott picks up on the homicidal werewolf's feelings of anger. Peter traces the spiral on the condensation on the window of Scott's car leaving a message for Scott.
Derek begs Peter further, asking if anyone else survived the fire. He pleads with, begs Peter to show him some sign of recognition, to give him something. Jennifer then scolds Derek for yelling at his uncle. Derek leaves.
Peter then goes out to track his nephew and Scott.
Later at night, Scott has comes up with a plan to call Peter to the high school with a howl to try and prove to Derek that Alan Deaton isn't the murderous Alpha.
Peter has his accomplice send Allison a text posing as Scott asking her to meet him at the school, and an anonymous tip to the cops that there will be prank calls from students breaking into the school later that night+.
The Alpha has Scott and Stiles trapped. He howls, having them retreat further into the school. He disables Stiles's Jeep by bending the hood, and pulling out the battery. He then taunts the two boys by throwing the battery into the chemistry classroom.
Scott and Stiles take refuge in the locker room, but a janitor catches them. Peter kills the janitor and then hides the body in the school's gym.
When the five teenagers are finally grouped together, the alpha continues to stalk them, chasing them throughout the dark, deserted school. He has the five teenagers thinking he's going to kill them. He traps them in the chemistry classroom. Scott finally catches on that the Alpha is actually corralling them, figuring out he could have killed them at any time what with his speed and power.
Scott eventually walks out, head high to confront his werewolf sire, armed with a self-igniting Molotov cocktail concocted by Lydia. His sense of smell leads Scott to the gym as the Alpha had planned. The more powerful werewolf waits then charges Scott who throws the cocktail. Unfortunately, because Lydia had missed a key ingredient, the firebomb fails.
Scott, under Peter's thrall, walks back to the chemistry classroom fully intending to savage and murder his friends. The whole attack was a ploy by Peter to get into Scott's head, then have him kill his best friend Stiles and his girlfriend Allison, to again have Scott become a killer, to have him evolve as a werewolf. Jackson and Lydia were just accidental bystanders. However, Allison's voice prevents Scott from hurting anyone. When Scott breaks Peter's control over him and the police show up, Peter retreats.
A few days later, the night before the full moon, Peter tracks two crooks in the Beacon Hills Preserve. He recognizes the two men as two other arsonists he'd seen set the Hale House aflame with gasoline the night of the fire+. The Alpha kills one of the men by maiming him. He then attacks the second thug by grabbing him by the ankle. He then dumps the man's body into a barrel that's being used as a fire pit and lets the man burn alive screaming.
After experiencing the full moon, the alpha is seen atop Lookout Point, morphing back into his human shape.
Harris is working late at school, and Peter comes up behind him. Peter has left a note on his desk. Harris stammers with fear, knowing what the list being on his desk means. Peter asks Harris who wrote that list. Harris immediately answers it was Laura Hale. The Alpha taunts Harris that he knows something about why he's here. Harris, knowing what's happening, pleads and begs for his life. Peter taunts Harris to turn around. Before the Alpha can do any harm, Derek shows up and stops him from harming Harris, before the police show up tracking Derek.
Stiles, with Danny Mahealani's help, is able to trace the text that went to Allison's phone the night of the attack at the school to a computer logged in under Scott's mother's account. This leads him and Derek to the Beacon Hills Hospital. Stiles curiously sees that Peter isn't in his room. Derek finally realizes that Peter is the Alpha. Peter, knowing his gig is up, introduces himself to Stiles.
Peter and Nurse Jennifer reveal themselves as the culprits behind the attacks and murders. Derek rescues Stiles, knocking out Jennifer to which Peter scolds his nephew. Peter questions Derek does he really think he'd kill Laura, his niece, on purpose. Derek outraged, attacks Peter, but the alpha easily overpowers him, parrying every strike then thrashing Derek. Peter professes a speech to his nephew about how the fire crippled him for years, taking him all that time to heal. He softly admits that becoming an alpha, taking the power from Laura pushed him over a plateau in the healing process.
Peter: I was going to wait for dramatic flair, but ... when you look this good, why wait?
Peter convinces Derek to allow him to explain his actions, reasoning they're family. Peter lures Derek to join him in his quest for revenge. He claims that Laura's death at his hands was a mistake and appeals to Derek that during his six-year-long coma his mind and his personality were "burned out of him."
They come upon Scott in the locker room under a cover of darkness. Peter reveals his human identity to his werewolf progeny and attempts to outright convince Scott to join him. Scott refuses to help Peter continue his murder spree. Derek tells Scott Peter's story that he killed Laura but by accident, the elder wolf apparently played upon his instability from his coma for sympathy. Peter tells Scott the young man simply has the wrong impression of him. He wishes to have "(Scott) reach his full potential". He plants his memories of the fire, his coma and everything else upon Scott to have him see things from his perspective. Leaving his beta writhing in pain on the floor, Peter exits the high school.
Scott still refuses to join Peter, even if the people he murdered were criminals. Peter decides to use a different tactic. He poses as a pharmaceuticals rep and asks Melissa McCall out on a date. She's utterly thrilled. Scott sees Peter at the door, then is completely horrified. Peter malevolently mocks Scott's "impotent sounding threats" and lets his beta know it might be easier for Scott to be part of the pack if his mother is too, intending to bite Melissa. Peter softly reminds the younger wolf that their kind are much stronger while in packs, comparing the concept to the Wolf Pack German boat attacks during WWII. Scott can only stand by as Peter takes his mother out and is unable to say anything, other than "have a good time.".
Peter parks his car near a grove of trees. He makes a move on Melissa, complimenting her on her skin. Distracted, Melissa drops her makeup case. Peter then is about to strike, shifting his teeth into his fangs, zeroing in on Melissa's blindspot.
Peter conspires with Derek to intimidate Jackson into silence. Scott, assuming they had meant to kill Jackson, runs to his rescue which results in Derek getting captured by the Argents.
Alan Deaton apologizes and tells Peter the vet is closed. Peter informs the vet he's here to pick up (Scott). Deaton is unafraid, and stands stoic telling the alpha "they're closed." Peter moves in to strike, but picks up he's being repelled by mountain ash, realizing Deaton is more than he appears to be. He throws a chair against the wall in anger, but ultimately relents. As he's leaving, he softly threatens Scott that there are others that will provide leverage over Scott into his helping him get Derek back. Scott realizes he's going after Allison.
At the winter formal, Peter is in the crowd, but blends in. As the night goes on, Lydia wanders off onto the lacrosse field. Peter has the field lights turned on, blinding her and providing cover. He approaches her, just as Stiles is running onto the field trying to warn her.
Peter shifts, manifesting his fangs, then bites Lydia in the side, leaving her unconscious. Peter knew that the bite would awaken Lydia's latent banshee powers and establish a connection between them as a backup plan in case he were to die+.
In desperation, Stiles comes up with an idea that Derek had known that he'd be taken by the Argents, so Stiles hurriedly surmises that he took Scott's phone, because it has GPS, so they could find him.
Peter forces a distraught, worried Stiles into coming with him. He allows Stiles to call Jackson to come and get Lydia. He then has Stiles drive him in his jeep. Peter, not giving away his backup plan, assures Stiles that if Lydia lives, she'll become a werewolf. Stiles sarcastically answers she'll also go out of her "freaking mind" once a month and try to tear (Stiles) apart. Peter jokes that Lydia is a woman, so actually "twice a month."
Peter: "His username is Allison?" (Stiles types). "His password is also Allison?"
Stiles: "Still want him in your pack?
The GPS coordinates reveal that Derek is at the Hale House, Peter figures out Derek is actually in the tunnels beneath the house. He hears both Scott and Derek howling, realizing Scott can also find Derek. Peter crushes Stiles' keys to prevent him from following. After Stiles snarks at Peter's playing the victim. Peter then lazily offers to give Stiles the bite, going for his wrist. At the last second Stiles refuses. Peter tells Stiles that he's lying to himself that he doesn't want it, but Stiles still refuses. Peter accepts his refusal and heads off to the Hale residence.
Peter arrives at the Hale House just as Chris has stopped Kate from killing Scott and has confronted Kate about her orchestrating the Hale Fire. Peter throws himself out of the house at his highest speed. He knocks Chris Argent unconscious, disarms Allison and thrashes Scott. Peter gets the better of Kate, restraining her by breaking her arm and tossing her into a painful landing. He then drags her into the house.
Peter taunts Kate over Allison's innocence compared to her. Seething in a dangerously soft tone, the werewolf gives Kate a chance to save her niece.
Peter: "Apologize. Say that you're sorry for decimating my family. For leaving me burned and broken for six years! Say it. And I'll let her live.
Kate, stammering gasps out an apology, but it's obvious she's only talking to Allison. Peter settles into a lazy smile then rips Kate's throat out, spiking her with his memories of the Hale Fire out of spite, swiftly killing her.
The two betas take on the alpha together, but are outmatched. After knocking Derek unconscious, Peter solely engages Scott. Throwing the beta aside, Peter fully transforms into his beast werewolf form. He takes the fight with his werewolf progeny outside, still having the advantage.
Peter: "You've already decided. I can smell it on you."
Derek glares at his uncle. He then kills Peter by slashing his throat, over Scott's protests, taking his alpha status.