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

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

Stiles works on tracking down a fugitive; Liam tries to be Mason's wingman at a nightclub.

In hopes of learning more about the Dread Doctors, the pack goes into Eichen House.

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

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

Upon learning that Lydia is in danger, Stiles makes a plan to break her out of Eichen House; Theo has his own plans.

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