In Beacon Hills, high school seniors Scott McCall, a werewolf who wants to protect his pack, and his best friend Stiles Stilinski, who wants to keep everyone safe, face a new threat. Mysterious figures known as the Dread Doctors are creating dangerous Chimeras, creatures with the DNA of multiple supernatural beings. Their goal is to create a "perfect" Chimera, and they begin experimenting on local teenagers, including Liam Dunbar, a new werewolf, and Hayden Romero.

The season's central conflict revolves around the Dread Doctors' experiments and the emergence of a powerful, monstrous entity known as the Beast. Theo Raeken, an old acquaintance of Scott's, returns to town, seemingly offering help but secretly working with the Dread Doctors to gain power. As the season progresses, the Dread Doctors' experiments lead to escalating violence and death. Key turning points include the accidental death of Donovan by Stiles, the Dread Doctors terminating Tracy, and the shocking revelation that Mason is being used as the Beast's host. The pack struggles to understand the Beast's origins and how to stop it, facing internal conflicts and betrayals.

The season culminates in a desperate battle against the Beast and Theo's machinations. Major deaths include Hayden and Tracy. Ultimately, the pack manages to defeat the Beast and banish Theo, but not without significant loss and the lingering threat of future dangers.

Season 5 of Teen Wolf covers episodes 1-20. Here's everything that happened:

Season 5, Episode 1: Creatures of the Night - The episode opens with a flash-forward of Lydia in Eichen House, foreshadowing a dark future. Scott and the pack prepare for senior year, but a new werewolf, Belasko, seeks to steal Scott's Alpha power. Theo, an old friend, returns, offering help. Belasko is killed by the Dread Doctors after failing to steal Scott's power. The episode concludes with the pack at Senior Scribe, but Lydia's vision hints that her friends are all going to die.

Season 5, Episode 2: Parasomnia - Tracy experiences night terrors, leading to a disturbing transformation after an injection by the Dread Doctors. Stiles investigates Theo, suspecting he's not who he claims to be. Liam struggles with keeping his werewolf identity from Mason but ultimately reveals it when a black wolf appears. The episode concludes with Tracy revealing her werewolf form.

Season 5, Episode 3: Dreamcatchers - Scott tracks Tracy, a new shapeshifter, while Stiles investigates Malia's mother. Tracy, suffering night terrors, escapes custody and kills her own father. Deaton discovers Tracy is a Kanima, not a werewolf. Malia fights Tracy, but the Dread Doctors arrive and terminate Tracy. The episode concludes with the aftermath of Tracy's actions and the growing threat of the Dread Doctors.

Season 5, Episode 4: Condition Terminal - Liam and Mason go to a gay club where Liam senses something is wrong. Kira loses control as a Kitsune while fighting Lucas, a new Chimera. The Dread Doctors kill Lucas, deeming him a failure. Stiles is attacked by Donovan, who now has a monstrous mouth on his hand. Parrish takes Lucas' body to the Nemeton.

Season 5, Episode 5: A Novel Approach - Stiles accidentally kills Donovan in self-defense during a library confrontation. The pack seeks answers about the Dread Doctors at Eichen House, where Lydia and Stiles meet Dr. Valack. Kira's powers surge, causing chaos. Malia confronts memories of the Desert Wolf. Donovan's body vanishes, setting up further mysteries.

Season 5, Episode 6: Required Reading - The pack reads Dr. Valack's book, triggering vivid, dangerous memories. Scott relives his asthma attack, and Malia recalls her family's car crash. Lydia realizes her Dread Doctor memories aren't hers. Theo kills the Chimera Josh, blackmailing Stiles. The episode ends with Liam discovering Hayden's Chimera status.

Season 5, Episode 7: Strange Frequencies - Scott's plan to protect Hayden involves using her as bait, angering Liam. Stiles helps Theo cover up Josh's murder, fearing the consequences. The pack experiences gruesome hallucinations at school. Liam and Hayden are kidnapped by the Dread Doctors. Melissa finds a body impaled with Kira's sword in her kitchen.

Season 5, Episode 8: Ouroboros - Scott and the pack race to rescue Liam and Hayden from the Dread Doctors. Kira's increasing instability leads to her arrest, but her father confesses to protect her. Kira and her family leave Beacon Hills. Meanwhile, the Desert Wolf confronts Deaton, seeking Malia. Theo rescues Liam and Hayden. The episode concludes with Scott realizing something has changed within his pack.

Season 5, Episode 9: Lies of Omission - Scott's asthma returns as the pack fractures, each keeping secrets. Theo manipulates Scott by revealing that Stiles killed Donovan, twisting the story to paint Stiles as a murderer. Corey, another Chimera, is killed by the Dread Doctors. Lydia helps Parrish realize he's been taking the dead bodies to the Nemeton. The episode concludes with Scott confronting Stiles about Donovan's death, their friendship strained by Theo's lies.

Season 5, Episode 10: Status Asthmaticus - Scott is trapped by Theo, who reveals he's the first Chimera. Liam, fueled by the supermoon, tries to kill Scott after Hayden's condition worsens. Stiles chooses to find his injured father instead of helping Scott. Hayden dies, and Melissa revives Scott. The Dread Doctors reveal their success.

Season 5, Episode 11: The Last Chimera - Scott and Stiles work to save Sheriff Stilinski from a mysterious poisoning. Lydia is at Eichen House, undergoing a procedure with Dr. Valack to uncover Theo's secrets. They discover Theo killed his sister for a heart transplant, making him the "perfect killer". Chris Argent returns to help the pack. At the end, Lydia is committed to Eichen House.

Season 5, Episode 12: Damnatio Memoriae - Scott seeks to rebuild his pack, while Theo manipulates his own resurrected chimeras. Stiles confesses to his father about killing Donovan. Tracy murders her father in the hospital. Scott and Stiles investigate the Beast, realizing it's a resurrected creature. The episode concludes with Theo proposing a truce with Scott to face the Beast.

Season 5, Episode 13: Codominance - Kira and her mother seek help from Skinwalkers to control her Kitsune spirit; however, Kira fails the Skinwalkers' test. Scott and Stiles reconcile and head to New Mexico to help Kira. Theo and Tracy search for the Beast, and Malia confronts Theo about Deaton. The episode concludes with the pack escaping the Skinwalkers and Mason revealing that Theo is seeking Deucalion.

Season 5, Episode 14: The Sword and the Spirit - Scott tries to reunite his pack while Malia, with Braeden and Theo, seeks to rescue Deaton from the Desert Wolf. Lydia awakens in Eichen House and attempts to escape, using her banshee scream. Theo's duplicity is revealed when he betrays Malia, and Deucalion returns, offering Theo help to steal the Beast's power. Ultimately, Malia saves Deaton, and the pack unites to rescue Lydia from Eichen House.

Season 5, Episode 15: Amplification - Stiles learns Lydia is in danger at Eichen House and plans a rescue. Scott, Liam, Malia, and Kira work together to breach the facility, while Parrish confronts the Beast. Stiles finds Lydia with a hole drilled in her head, courtesy of Dr. Valack. Lydia warns Stiles to leave, but Eichen House goes into lockdown, trapping everyone inside.

Season 5, Episode 16: Lie Ability - Scott and the pack, trapped in Eichen House, race to rescue Lydia from Theo and Valack. Scott gleans information from Meredith's mind, learning that Parrish is key to finding Lydia. Stiles and Theo reluctantly team up, while Lydia uses her banshee scream to kill Valack. Ultimately, Lydia is saved, and Theo obtains the Dread Doctor's mask.

Season 5, Episode 17: A Credible Threat - Scott's pack uses a charity lacrosse game to identify the Beast. Parrish, seeking control over the Hellhound, gets help from the Argents and Lydia. Malia faces the Desert Wolf. The lacrosse game proceeds, and the Beast attacks, running rampant. Lydia connects with the Hellhound, and Parrish realizes he must leave.

Season 5, Episode 18: The Maid of Gévaudan - Gerard recounts the tale of Marie-Jeanne Valet (Crystal Reed) to Lydia, revealing the origins of the Beast. In 1760s France, Marie-Jeanne confronts the Beast, who is revealed to be her brother, Sebastien. Meanwhile, at Beacon Hills High, Scott and the pack battle the Beast, with Scott managing to get its scent. The scent leads them to Mason, who is then taken by Corey, solidifying Mason's role as the Beast's host.

Season 5, Episode 19: The Beast of Beacon Hills - Scott and his pack race against time as Mason's connection to the Beast intensifies after the Dread Doctors connect him to a Nazi werewolf. Theo, manipulated by Deucalion, kills Josh to absorb his power. When the Beast emerges, it's not fully Mason, but Sebastien Valet. The episode concludes with the Argents seeking the pike to kill Sebastien.

Season 5, Episode 20: Apotheosis - Scott and his pack race to stop the Beast, with Deucalion and the Argents offering uneasy alliances. Theo kills Tracy to steal her power, while Malia confronts and defeats the Desert Wolf. Ultimately, Lydia uses her banshee powers to help Mason return, and Kira returns to help banish Theo to hell.