When a new threat proves to be more powerful than anticipated, both The Pack and Coven suffer heavy losses in the confrontation.

Elena awakens to find herself the subject of painful tests in a hidden compound run by a maniacal and powerful cult leader. Meanwhile, The Pack and witches must resort to dark magic in an effort to track down their missing members.

In order to stay alive, Elena must guide Dr. Bauer through her first Change as The Pack and Coven try to figure out who Aleister is, and where his compound is located.

Aleister casts a mind-bending spell on Elena, forcing her into a battle against her own dark fears and demons. Meanwhile, Rachael is locked in a cage with Logan, struggling to come to terms with what he is. In a nearby forest, Clay and Paige must overcome their personal differences in order to find Aleister’s compound.

When the new Spanish Alpha tries to blackmail Jeremy into murdering the Russian Alpha, the Pack has things under control until a surprise visit from Savannah upends their plans. Nick and Paige try to secretly meet Nick's mother.

Rachel and Logan battle their own demons as Aleister’s Undoing takes hold of the witches and has unexpected consequences for the wolves. The Pack and the Coven do their best to defeat him before sunrise—when life as they know it will change forever if Aleister and Clara get their way. A reluctant Ruth resorts to Left Hand magic to fight her son while a surprise ally appears to offer help to Jeremy and his Pack.

Elena and The Pack storm the Delphi building to save Savannah, the witches, and the werewolves in a final showdown against Aleister and Clara.