When Lydia goes missing from the hospital, werewolves and hunters begin a search. Isaac, a tormented teen abused by his father, is attacked while working in his father's cemetery. 

Isaac's father is murdered by a strange creature and he is taken into custody. Scott, Stiles and Derek plan a break-out. 

It's time for Allison to wake up and smell the wolfsbane as hunter-wolf hostility plummets to sub-zero. Scott confronts Derek's pack but gets a frosty reception. 

The new shape-shifter strikes again, and Scott recruits a reluctant Allison to acquire a rare book in Gerard's collection. 

Convinced that Lydia is the Kanima, since she displayed immunity to the creature's toxin, Derek wants to kill her. Scott, Allison, Stiles and Jackson try to protect her together.

Both Derek and the Argents have a pop at bringing down the Kanima. Can anyone control it? Meanwhile, Scott and Stiles try to protect the teen trapped beneath its scaly skin.

Lydia begins to make connections about the bite from Peter, causing new problems for Scott and Stiles. Meanwhile, Derek has a crisis of faith in his leadership as a new alpha.

Scott and Stiles develop a plan to trap the new shapeshifter, while Allison's mother comes up with a plan of her own to take care of Scott once and for all.

Scott and Stiles attend Lydia's birthday party; Scott's relationship with Allison is strained; Derek locks the new wolves up.

While compiling evidence to incriminate the puppet-master behind the Kanima, Scott and Stiles are taken hostage; Allison has murder on her mind and targets a wolf.

Scott helps win the championship lacrosse game; the wolves are attacked on all fronts and Boyd and Erica leave Derek, terrified of the Argent werewolf genocide.

Scott races to uncover Gerard's master plan following a shocking death on the lacrosse field. Meanwhile Derek plots to take Gerard down using his own methods.