Scott tries to keep Derek from creating new werewolves; Argent officially begins Allison's training; the new creature in town takes another victim.

When the new shapeshifter strikes again, Scott has to recruit a reluctant Allison to acquire a rare book in Gerard's collection, while also once again surviving dinner with her family.

Derek becomes convinced that Lydia is the shapeshifter they're after, forcing Scott to gather his friends -- and even some enemies -- to protect her.

As Lydia begins to make connections about the bite from Peter, Jackson causes new problems for Scott and Stiles while Derek has a crisis of faith in his leadership as a new Alpha.

During a secret concert, Scott and Stiles come up with a method to trap the new shapeshifter. At the same time, Allison's mother comes up with a plan of her own to take care of Scott once and for all.

Even as his relationship with Allison becomes further strained, Scott and Stiles must attend Lydia's birthday party while Derek locks his new wolves up to watch after them on their first full moon together.

Scott plays in the championship lacrosse game and must figure out a way to stop Gerard. Meanwhile, Allison continues her hunt for Derek and his pack.

Scott races to uncover Gerard's master plan following a shocking death on the lacrosse field. Derek plots to take Gerard down using his own methods. Erica and Boyd are captured as Allison continues her merciless bloodthirsty revenge on the werewolves for her mother's suicide. Meanwhile, Scott, Stiles, Lydia, Melissa and Isaac are all under pressure amidst the chaotic events.

Allison and Lydia locate a possible clue to finding Boyd and Erica while one of Stiles' childhood friends goes missing.

With Boyd and Cora on the loose and under the influence of the full moon, Scott and Derek must turn to an unlikely ally for help.

As the danger begins to reach closer to Scott, threatening his trusted mentor and boss, Deaton, Kali and the Twins go after Derek.