On the eve of the start of senior year, Scott and his pack are challenged by the arrival of a new enemy.
Stiles tries to prove his suspicions about a new classmate; Lydia helps a student who suffers from night terrors.
Scott tracks a dangerous shapeshifter that has been threatening Stilinski; Malia receives information about her mother.
Stiles works on tracking down a fugitive; Liam attempts to be wingman for Mason while at a nightclub.
The pack enters Eichen House in order to learn more about the Dread Doctors.
Scott and his friends follow Dr. Valack's advice; and experience strange effects as a result.
Scott's plans to protect the newest victim are derailed when The Dread Doctors attack.
Scott and Malia try to rescue captured friends; Deaton discovers something horrific about The Dread Doctors.
Scott turns to an unlikely ally for help; and Stiles and Lydia seek the truth about Parrish.
Scott and the pack face what may be their biggest threat yet.
Scott and Stiles try to learn what is behind the mysterious infection that is killing the town sheriff in spite of their deep rift.
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; Lydia is surprised at Eichen House.
Scott tries to put his pack back together; and Malia and a new ally set out to rescue Deaton from the Desert Wolf.
Stiles learns that Lydia is in imminent danger and develops a plan to break her out of Eichen House. Theo, however, has his own plans for her.
Scott hopes to rescue Lydia, who's trapped in Eichen House with Theo and his Chimera Pack.
Scott and the pack try to use a charity lacrosse game to figure out the identity of the Beast.
The Argents share an important clue about the mystery of the Beast of Gevaudan; and Scott tries to take on the Beast by himself.
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.
Scott and his friends try to stop the Beast before Beacon Hills is razed to the ground.