Theo is beside his car on route 115 where there is a massive car pileup along the road. Two cars behind him is the Yukimuras' car.
Theo is present and looks on as the Dread Doctors appear using their power to create a vast mind-control field over the immediate area and as they come upon Kira whilst wiping her memory blank rendering her oblivious to what's currently happening to her, heightening her kitsune power so to use her as the ace in the hole for their plan of assault against Scott's Pack+.
Theo: (Flashes a smile, raises his phone) "'Not getting anything either.
Kira: (Smiles back)
A while later, Theo looks on as Kira runs out of her car, she and Scott jubilantly greeting each other and kiss from the inside his car.
Theo follows the couple to the Beacon Hills high school.
Scott and Kira are fighting off the Chimera Belasko, whom is another agent of the Doctors. Just as the other paranormal is about to stab Scott with his talons, Theo appears jumping off the underpass as a werewolf. He ferociously engages Belasko, luring him away from Scott so he can preserve the chance to take Scott's power for himself. Theo joins in the fight alongside Scott and Kira. Belasko gains the upper hand, slugging both he and Kira and regroups alongside her.
Theo shifts back into human form, smirking, saying Scott doesn't remember him. He admits he looks different since the fourth grade. At that, Scott recognizes Theo who's been away for a long time. He says he's returned because a few months ago he'd heard of an Alpha in Beacon Hills, California and that his name was Scott McCall, his friend from grade school. Theo is amazed that Scott isn't just an Alpha, he's a True Alpha.
Theo: "I came back to Beacon Hills. Back home with my family. Because I want to be a part of your Pack."
Theo is dropped off at the high school for the first day of senior year. He looks ahead and sees Stiles Stilinski and Malia Tate up on the steps and gives them a wave. He is also in AP Biology with Scott, Kira and Lydia.
Scott and Stiles meet with Theo in the boys' locker room in between classes. At Stiles' urging, the two of them ask Theo for his story, specifically how is he a werewolf.
He'd been skating in a neighbour's pool, he was so determined to do great, he didn't realize it was past night. His last try at a hand plant, he landed flat on his back, but he realised he never heard his skateboard fall back down. Theo'd looked up and saw his board in the clawed hands of a sihouette with glowing red eyes. It came at Theo fast and he tried to run when he was Bitten in his side. Stiles asks him why didn't the Alpha come back for Theo and he isn't part of his Pack.
Theo: "By the time of my first full moon ... he was dead. ... killed by two of his own Betas. They were twins."
Scott and Stiles share a look. Stiles is skeptical, saying Theo may not be who he says he is. Theo placates Stiles that he is the same kid he remembers back in the fourth grade with them. He remembers a day where he saw Scott in the nurse's office where they both had an inhaler and Scott took pity on him and comforted him during breathing problem. Theo appeals to Scott that he's been on his own, that lone Wolves don't survive, and he's hoping Scott was still that same kid. Scott listens whilst Stiles rolls his eyes at Theo's speech, still suspicuous. The bell rings and Theo leaves needing to get to class.
After schhol at night, Theo parks his car outside the Preserve and takes a wrapped package out of the boot. Stiles and Liam are spying on him after watching Theo play video games in his room for the past three hours. They follow Theo into the woods with Theo acting he's unaware of their presense, listening to them. Theo stops on top of the bridge where his sister died. Stiles and Liam catch up to him and observe his emotional state. He drops a flower into the river, imitating feelings of grief, paying respects to his late older sister. He knows the other boys are backing away
Theo then runs up ahead of Stiles and Liam in minutes and makes a dramatic entrance. He lays on the charm again asking them what are they doing.
Liam acts territorial though Stiles keeps a grip on the younger Wolf. Theo quickly takes note of Liam's superior strength. Theo tries to placate Stiles again asking why is he so suspicious of him.
Theo then tells Stiles he doesn't have anyone like him or Scott. He did come back for Scott specifically but also for Stiles. Someone who is willing to go off into the woods searching for his best friend.
Theo: "I know I'm in the right place. I'm meant to be here. I'm meant to be a part of this Pack.
Theo appears behind Liam, shapeshifted into a full black wolf. Once both boys notice the wolf's presence, Theo snarls at them, then chases them into the high school.
The boys run into the high school. Liam stops running, his anger building up. As the wolf advances, Liam turns around, shifts and roars at the wolf. Theo feigns submissiveness and retreats out of the school. He hears Mason realising Liam is a werewolf.
His objective accomplished, Theo appears back at the bridge. He shapeshifts back to human form. He thinks of the current state of Liam and Mason's friendship, looking back with a mischievous smirk.
Theo is now at his parents' house.
Theo: "There is one way a false signature can be explained." (Produces a hammer.) "It's not easy to write when you're wearing a cast. Is it?"
The man is terrified, but Theo unsympathetically indicates the man to place his hand on the table. The man closes his eyes, complying and whimpering. Theo brings the hammer down, smashing the man's hand.
Theo overhears Stiles conversing with his father, the Sheriff, speculating that maybe Donovan didn't commit the carnage, indicating he suspects Theo is responsible. Theo disappears.
The next day at school, Theo continues to keep an eye on everything going down. In AP Biology, Mrs. Finch is asking Scott to read out the homework of last night. Theo notices that Liam is trying to get Scott's attention, so he talks to Scott using the latter's Wolf hearing. Theo listens as well as Liam relays that Tracy is in Liam's sophomore history class.
Theo looks for Scott and the others and finds he, Stiles and Alan Deaton at the animal clinic, paralyzed after being slashed by Tracy. Theo tells Scott he found him because he works there and he'd heard about Tracy. Theo implores them to let him help them, promising it doesn't have to mean he's in the Pack or he's been accepted or anything like, just that he wants to help.
He and Stiles see that Lydia has been fatally wounded in the side by the kanima hybrid with Kira applying pressure. Theo immediately runs over to assist and takes out his belt wrapping it under and around her, using it as a tourniquet. Natalie comes up from the basement and worriedly rushes over to her daughter. Theo, Kira and Natalie stay with Lydia, Theo promising Stiles Lydia will be OK, while Scott, Stiles, Deaton and Stilinski inspect the basement.
Once the situation has been contained, Theo inconspicuously steals Donovan Donati's application folder.
At the hospital, Lydia is hospitalized and everyone including Theo, regroups to talk about what to do next. Melissa updates everyone on Lydia's condition and praises Theo for his quick thinking with his belt that he probably just saved her life. Theo catches Stiles giving him a silent nod of acknowledgement.
In AP Biology the next day, they are studying DNA strands. Theo answers Mrs. Finch a question correctly: "Nucleotides."
In the Dread Doctors' operating theatre, Theo arrives and visits Donovan who the Doctors have just converted into their next test subject, a wendigo with traits of a lamprey.
Donovan: "Decide what?!"
Theo: "Whether or not you die."
Theo then shows Donovan his psyche evaluation from when he took his test to be a sheriff's deputy. He gets further under Donovan's skin, lecturing him. Theo explains the definition of a multiphasic personality inventory which determines whether someone is lying, being defensive or if they're a total psycho. Theo notes he failed miserably, scoring high on the psycopathic deviate scale and his anger expression inventory notes that he is "not suitable for law enforcement." Donovan is ticked off when Theo laments that he now can't be a cop like his father.
Theo then cranks up the examination table and removes the head casing, now showing him sympathy. He nonchalantly goes on to say that Donovan has something else now instead; he has power, explaining he now has super-strength, speed, heightened senses which catches the delinquent's attention.
Theo: "The problem is though, sooner or later, physical pain ... it's manageable. See, real pain is emotional pain. That is the kind of pain that lasts. And if you want to cause Stilinski devastating, soul-crushing emotional pain, you don't go after him. You go after someone he loves."
Theo maniacally grins when his words easily get to Donovan, that he should kill Stiles. He sets Donovan free and follows the delinquent as he tracks Stiles down.
Theo keeps to the shadows as Donovan assaults Stiles, chases him into the high school. He gives Donovan his key card so the psycopathic Chimera can access the library where Stiles is hiding. He watches and listens as in the end, Stiles accidentally kills Donovan in self-defence. After Stiles leaves the library in an emotionally distressed state, Theo searches the library and takes the wrench Stiles had used to smash Donovan's head in trying to escape, then follows the other young man out of the library. Later both he and Stiles separately notice that someone had swiftly cleaned up the library and had taken Donovan's body++.
Scott: "' .... this book is dedicated to - Dr. Gabriel Valack!'"
Theo: "Do you know him?"
Scott: "Yeah. And I know where to find him?"
Theo learns Scott, Stiles, Lydia and Kira are going to Eichen House to see Valack as according to their plan at night. Theo appears at the operating theatre and reports to the Doctors that their trick planting the book worked and that the Pack is going to see Valack at Eichen House later at night.
While the Pack visits Eichen House, Theo joins Malia in the school library where she is hunched over the novel. Theo whips out his calculus text for study. The two share inquisitive looks: Malia suspicious and Theo charismatic.
Hours later, after Malia finishes up, Theo offers her a ride. Malia said she can take the bus, or walk. Theo remarks that he's seen her coming out of driver's education, to her chagrin.
Theo: "Pretty sure I saw you destroy a couple of traffic cones the other day. And nearly take out a sophomore."
Malia: (stands defensive) "The sophomore shouldn't have been standing there."
Theo: (chuckling, takes out his keys) "Sounds like you could still use some practise."
He flicks her the keys to his car for a test run, she catches them just as swiftly and the two share some bold, charged looks.
Malia is steadily driving Theo's car down a rural lane, with Theo riding shotgun. He mocks her for going the speed limit and how she firmly grips the wheel. Theo covers her hand with his and encourages her to relax and go a little faster. Malia begins to relax but suddenly comes to appear a million miles somewhere else. Theo asks if she is OK.
Malia then staggers out of the car and falls to her knees for minutes. Theo keeps an eye on her. Suddenly another car is on the other side of the road. Theo immediately urges Malia to get up, grabbing her and throwing her along with him onto the other side of the road.
Malia is short of breath after recovering from the induced memory recovery as a result of reading the book. Malia confides in Theo she experienced her memory of when her family wwas on the road back home and had crashed into the Preserve, which triggered Malia's full transformtion, thereby causing her family's deaths. She tells him it wasn't an accident, that someone opened fire on her mom's car, and that it was the Desert Wolf. Theo keeps the information Malia just confided in him secret.