It's the eve of senior year and Scott and his pack deal with the arrival of a new enemy and the return of an old friend.

Stiles attempts to prove his suspicions about a new classmate are justified. Lydia attempts to help a student.

Scott tracks a new shapeshifter that's threatening Stilinski; and Malia receives information about her mother.

Stiles attempts to track down a fugitive. Liam works as one of Mason's wingman at a nightclub.

The friends enters Eichen House so that they can find out more about the Dread Doctors.

Scott and his friends decide to take Dr. Valack's advice and then experience some strange effects as a result.

Stiles is suspicious about a new girl showing up and what her intentions are. Scott's plans to protect the newest victim are derailed when The Dread Doctors attack.

Scott and Malia get help to try to find Hayden and Liam. Deaton discovers something horrific about the dread doctors. Hayden and Liam will be faced with a life and passing situation.

Scott finds himself turning to an unlikely ally for help. Stiles and Lydia attempt to find out the truth about Parrish.

Scott and his friends have to deal with what could be their biggest threat yet.

Scott and Stiles try to learn what is behind the mysterious infection that is hugging the town sheriff.

Even without the support of his pack, Scott considers what the Dread Doctors' success means for Beacon Hills.

Kira and her mother make a journey to help Kira deal with her dark side. Meanwhile, Lydia is surprised at Eichen House.

As Scott tries to put his pack back together. Meanwhile, Malia and a new ally set out to rescue Deaton from The Desert Wolf.

After finding out that Lydia is in danger, Stiles decides to try and break her out of Eichen House. Theo has plans of his own.

While trapped in Eichen House with Theo and the Chimera pack, Scott tries to rescue Lydia before time runs out.

Scott and the pack use a charity lacrosse game in a ploy to learn the identity of the Beast.

Scott, Stiles, Lydia, Malia, and Liam are trying to figure out how to defeat the Beast of Gévaudan that the Maid of Gévaudan, Marie-Jeanne Valet, faced in 1765. As Gerard Argent, recounts Valet's story to Scott's pack in hopes they can deduce the creature's weaknesses.

With the identity of the Beast finally revealed, Scott and his friends are in a race against time to stop The Dread doctors from implementing their final plan.

Loyalties are tested and new alliances forged as Scott and his friends work to stop the Beast before Beacon Hills is razed to the ground.