The Season 2 finale begins with Elena, Clay, Nick, Paige, Jeremy and Cain arriving in Boston for the final showdown with Aleister. Jeremy breaks the news about Logan's death as Nick struggles to control his transformation and Elena is haunted by a new "Dead by Dawn" premonition. For better or worse, they approach the sleek modern building, under which is The Catacombs and Ruth stationed in the Ritual Room.
Aleister put a spell on the front door to impede them, though Clay fixes that in a jiff by throwing something big and heavy at the glass, effectively shattering it ("Yeah, that works," muses Paige). Once inside, they're attacked by Aleister's brainwashed security guards and are separated: Elena & Paige, Clay & Cain and Jeremy & Nick.
Below them, Aleister taunts Ruth as he approaches the Ritual Room, pausing every now and then to double over in pain as his mother throws some dark magic his way. Aleister casts his own spell on Paige, which causes her to get nasty and attack Elena. Luckily, Elena talks her through it and Paige vomits up black bile, rejecting the magic and ceasing to sound like possessed Regan from The Exorcist.
As Jeremy and Nick fight off more of Aleister's security guard goons, Aleister and Clara reach the Ritual Room, which can only be opened by a coven witch. Luckily, they've got Savannah with them, and soon Aleister is face-to-face with Ruth, who unfortunately breaks her protective circle when she tries to cut Aleister to get a sample of his blood. Aleister finds that he has no power in this room, though when he snatches Ruth's green ring, all of his wounds disappear.
Meanwhile, Clay and Cain are stuck in a corridor, being fired upon by a trigger-happy Aleister goon. Not wanting Clay to suffer his own fate — life without the woman he loves — Cain rushes the security guard, taking several bullets but succeeding in snagging the goon's key card. "Go get her," a dying Cain tells Clay, effectively completing his kick-ass redemption arc.
Paige opens the door to the Ritual Room and Elena attacks Aleister, who stabs her in the stomach when she tries to talk Savannah out of her trance. With her last bit of strength, Elena pulls the blade out of her belly and uses it to cut Savannah's arm, allowing her to pull the mind-controlling insect from her body and smush it. Clara grabs Savannah and runs from the Ritual Room with Aleister as Clay enters to hold Elena one last time before she dies. Whoa!
As Clay prepares to turn into a wolf to track down Aleister (why stay human with his lady dead?), Ruth prepares to perform one final spell. Having retrieved her green ring from Aleister, she puts it on Elena's finger and prepares to bring Elena back … at the cost of her own life. Paige tries to stop her, but Ruth insists on going through with it, claiming it's the last thing she has with which to fight Aleister. A resurrected Elena runs after Clay as Ruth dies in Paige's arms. Double whoa!
In another part of the Catacombs, an enraged Savannah promises Aleister that she'll make him suffer for what he did to Elena and assures Clara there's no way she'll let her into her body. Just then, Clay-wolf arrives, though Aleister easily evades his attacks as he now has his powers back upon Ruth being dead. As Aleister deals with Clay, Savannah works her magic against Clara, choking her to death. As Savannah takes her talisman from the dead woman, Aleister works his magic against her, but the powerful little witch is able to cast a counter-spell, locking the mentor and the student into a stalemate.
Elena comes to the rescue, turning the tide as Aleister is forced to turn his attention to her, determined to destroy her once and for all. An exhausted and shaken Savannah manages to work a spell that renders Aleister briefly paralyzed, allowing Elena to swoop in and deliver the killing stroke. As the sun rises, Aleister finally meets the fate meant for him as an infant as Elena drowns him in a ritual pool.
The Undoing successfully foiled, Jeremy, Clay, Elena, Nick, Paige and Savannah greet the glorious dawn and reflect on their fallen friends and allies. Jeremy tells Paige and Savannah that they're bound together by this experience and he'll never turn them away should they ever need The Pack's help again. Paige, now the coven leader, tells Nick they need time to heal and build and thanks him for showing her what love could be (so, a sorta-breakup, then?).
Savannah is feeling responsible for all these deaths, though Elena tells her not to blame herself. "You always have a choice - don't ever forget that." However, as Elena takes Savannah's hand, she's suddenly struck with a new vision: herself, covered in blood, calmly sitting at Jeremy's desk as Stonehaven burns around her.
Elena's alarmed look to the camera ends Season 2 with one heck of a cliffhanger!