When Lydia goes missing from the hospital, werewolves and hunters begin a search.

Isaac's father is murdered; Scott, Stiles and Derek plan a break-out. At the same time, the Argent family remove the principal and Allison's grandfather replaces him. Scott senses that another werewolf is in the lacrosse locker room and plans to sniff them out, literally.

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.

The secret behind Derek's tattoo is revealed and the Alpha pack make their presence known. Derek and Isaac struggle to locate Erica and Boyd.

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.

While Scott tries to keep Isaac from engaging in a deadly confrontation with the Twins in school, Stiles attempts to prove his theory that the killings have nothing to do with werewolves.

During a bus ride to a cross country meet, Scott and his friends flash back to the events of a preemptive strike against the Alphas that has left several injured and possibly one or more dead.

Stranded at a motel for the night because of the postponed cross country meet, Scott and the others suffer strange experiences that cause them to believe members of their own group may the mysterious killer’s newest targets.

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

As Allison begins to suspect someone dangerously close to her may be involved in the murders, Scott and Stiles conclude that Lydia’s rising talents may be their best bet to solving the murders.

Trapped inside an evacuated Beacon Hills hospital by a powerful storm, Scott and Derek must defend themselves against the Alphas while trying to figure out how to save Cora’s life.

With the threat growing far more personal and time running out on innocent lives, Scott is forced to make a difficult choice in order to save both friends and family while, at the same time, Derek and Peter try to figure out how to save Cora’s life.

Under Deaton’s advice, Scott and his friends use an ancient but extremely dangerous ritual to help them both save the lives of the people they love and stop Deucalion from achieving his sinister goal.

Scott, Stiles and Allison suffer side effects from the ritual sacrifice; Sheriff Stilinski searches through old cases.

Scott and his friends ponder catching the werecoyote before it is hunted down; an unlikely ally helps Derek and Peter break out.

On the night before Halloween, Mischief Night, a convicted murderer brought to Beacon Hills Hospital for surgery escapes, forcing Scott and his friends to step in to help when his unexpected target becomes clear.

Beacon Hills is under curfew from the power outage; the teens throw a blacklight Halloween party; Scott tries to earn Kira's trust.

Scott's friends pledge to protect him against an increasingly hostile enemy while Argent, Isaac and Allison search for answers through an old adversary from the Japanese Yakuza. At the same time, Stiles enlists Melissa's help in figuring out exactly what's going on with him.

Stiles goes missing; Scott and the others set off on a search; Lydia tries to master her new abilities.

Scott and the others try to prevent a disaster; Lydia and Allison seek out an unlikely teacher.

Scott and Lydia join forces. Meanwhile, Stilinski faces a review board.

Kira faces an unexpected enemy.

Scott and Derek call upon their friends and allies to make a last stand.