Aleister tells Elena that she's "the most powerful werewolf" and her blood is needed for something called "The Undoing." He gives her that mark on her neck to make sure she doesn't run too far should she ever manage to escape.
Aleister's resident mad scientist, Dr. Sondra Bauer, is fascinated by Elena, saying she will "open the gate to the Undoing." Her seemingly respectful manner makes for a stark contrast to the painful experiments she performs on her test subject.
Aleister continues his charming corruption of Savannah, telling her she's kept locked in her room to keep her safe from her new werewolf neighbor and encouraging her to use her left hand when wielding her abilities. Savannah's getting more powerful every day.
Back at Stonehaven, Paige's protests of Ruth's plans to utilize dark magic on Melanie Lau go unheeded. Ruth also reveals that Aleister is a witch himself ... which means someone broke something called 'The Commandment.'
... and Richard, the mutt she interrogated in Episode 1, in another. Richard is enraged that Elena gave him up to these "sadistic bastards" and all too willing to engage in Sondra's experiment to "observe combat": in theory, Elena will have to turn into a wolf to defend herself against Richard's attack.
Back at Stonehaven, Ruth has managed to make contact with the spirit of Melanie Lau, who speaks of "Fresh daises" and "We harvest the purple seeds to purge our sins for The Undoing" and "I feel sick ... I need to see Dr. Bauer." Fearing for Ruth's own life as the experience gets more intense, Paige breaks the connection.
Sondra now has Elena's wolf blood, though she's still dissatisfied with the results of her experiments -- Elena's blood should be 'attacking' Savannah's witch blood, but it's not. After pausing to consider a new course of action, Sondra fills a syringe with Elena's blood ...
The episode ends with Aleister and Sondra having sex in a circle of candles, watched by goons in hooded robes. During orgasm, Sondra injects herself with Elena's blood and Aleister gets off as she convulses in pain. Whoa.