|“|| Scott: "Whoa, whoa. We've got Econ. in five minutes."|
Stiles: "All right, did you forget the part about the family-murdering ax-murderer?"
Scott: "Did you forget that your dad is the Sheriff? He'd want us to stay out of it."
Stiles: "Are you kidding me? There's a family-murdering ax-murderer and we're not going to do anything about it?"
Kira: "Maybe we should just let the adults handle it..."
Stiles: "So the two of you just want to stay here at school and go to class? I've never heard anything so irresponsible in my life."
A high school student, Sean Walcott, searches for his cat, only to find it unharmed but covered in blood under his bed. Suddenly, he hears screaming and walks out to the hall to find a professional assassin known as The Mute has killed his parents and brother with a tomahawk. He instructs Sean to defend himself against him with a shard of glass, but instead, Sean jumps out the window and runs toward the hospital. The next morning, Derek and Peter meet with Braeden, who Derek hires to track down Kate to retrieve their stolen bearer bonds and learn the reason why Derek's Werewolf eyes are gold now instead of their usual blue.
At school, Stiles and Scott discuss the theft at lacrosse practice, where they see a new freshman, Liam, excelling on the field. Kira learns her parents are planning to move the family back to New York, a decision against which Kira strongly protests. Stiles and Lydia help Malia to improve her math skills. Scott's mom and Sheriff Stilinski learns of Sean's attack and decide to keep the kids out of it because they believed the case didn't have any supernatural elements. When Coach Finstock states that the team is having a "rebuilding" season, Scott and Stiles struggle to maintain their positions, while Liam continues to dominate the field. Scott, concerned about losing the captainship to Liam, accidentally plays too hard during two-against-ones and causes Liam to sprain his ankle. Meanwhile, Coach discovers that Kira has a talent for lacrosse herself and recruits her for the team.
After practice, Scott and Kira reaffirm their relationship, before he leaves with Liam for the hospital. Deputy Parrish and Lydia investigate Sean's house, where they find a hidden meat locker full of frozen human corpses. Sean, identified as a Wendigo, kills and devours one of the cops protecting him and proceeds to attack Scott's mom, but Scott arrives and saves her. Sean takes Liam hostage, and Scott tracks them to the roof. Liam breaks free and falls over the edge, but clings to the edge of the roof. Scott is restrained by Sean, and is forced to bite Liam's arm to keep him from falling. The Mute kills Sean and lets Scott live, only for the True Alpha to face the reality that Scott's bite may have turned Liam into his very first Beta Werewolf.
- Tyler Posey as Scott McCall
- Dylan O'Brien as Stiles Stilinski
- Tyler Hoechlin as Derek Hale
- Holland Roden as Lydia Martin
- Shelley Hennig as Malia Tate
- Arden Cho as Kira Yukimura
- Melissa Ponzio as Melissa McCall
- Linden Ashby as Sheriff Stilinski
- Ian Bohen as Peter Hale
- Orny Adams as Coach Bobby Finstock
- Meagan Tandy as Braeden
- Tamlyn Tomita as Noshiko Yukimura
- Glenn McCuen as Sean Walcott
- Joseph Gatt as The Mute
- Dylan Sprayberry as Liam Dunbar
- Mason Dye as Garrett
- Todd Williams as Dr. Geyer
- Tom T. Choi as Ken Yukimura
- Ryan Kelley as Deputy Jordan Parrish
- Rahnuma Panthaky as Ms. Flemming
- Kira becomes the first female student to join the Beacon Hills High School boys lacrosse team.
- Derek hires Braeden to track down Kate for him because he is concerned about his werewolf eyes turning yellow again. To do this, he had to pay her more money than Araya and Severo Calavera, who originally hired her to find Kate and bring her back to them.
- Noshiko and Ken Yukimura reveal that they plan to move back to New York now that Noshiko's mission of dealing with the Nogitsune is over. However, Kira cuts up the "For Sale" sign outside their home, which causes no one to come to the open house to find a buyer, leading them to end up staying in Beacon Hills.
- It is also revealed that Ken was previously a professor at Columbia University, an Ivy League university in Manhattan, New York.
- Christina Walcott - hacked to death; killed by The Mute
- David Walcott - hacked to death; killed by The Mute
- Michael Walcott - hacked to death; killed by The Mute
- Sean Walcott - stabbed in the back; killed by The Mute
- Walcott House
- Front Porch
- Sean's Bedroom
- Meat Locker
- Derek's Loft
- Beacon Hills High School
- Lacrosse Field
- Locker Room
- Ms. Flemming's Classroom
- Coach Finstock's Classroom
- Beacon Hills Memorial Hospital
- Reception Area
- Emergency Room
- Sean's Room
- Liam's Room
- Yukimura House
- Kira's Bedroom
- The Mute's Lair
- Beacon County Sheriff's Station
- Stilinski House
- Stiles' Bedroom
- "Dibby Dibby Sound" by DJ Fresh vs. Jay ft. Ms. Dynamite
- Liam demonstrates his abnormally good lacrosse skills at early-morning practice
- "Ruby (Original Mix)" by Deniz Koyu
- Kira and Malia talk about Kira's relationship with Scott while they watch lacrosse tryouts
- "No Defense Remix" by NOONE
- Scott and Stiles watch in awe and horror as Liam dominates everyone at lacrosse tryouts
- "Stargate" by Savant
- Scott and Stiles both perform disastrously at lacrosse tryouts
- "Work" by Jetfire
- Scott and Stiles team up against Liam and inadvertently cause him to sprain his ankle
- "Stakes" by Vancouver Sleep Clinic
- Scott and Kira passionately kiss in the hallway after tryouts
- "I Could Love You More" by The Miracals
- Malia and Stiles study together and kiss in Stiles' room