17. Know Thy Enemy

Complete story — includes the ending

Elena and Alaric become angry with John when Isobel's arrival devastates Jenna. Alaric is abducted by Maddox, a warlock from Klaus's inner circle. Meanwhile, Bonnie works with Jeremy and Damon to find the spell they need to gather the power of the witches killed in the massacre. Damon takes them to the site where the witches were burned. Matt demands to know what happened to Vicki. After Caroline tells him and then compels him to forget, it is revealed that Matt's involvement was a setup by Sheriff Forbes to find out everything about the vampires. Matt has drunk vervain, so the compulsion does not work. Isobel kidnaps Elena and then receives a phone call from Maddox, who tells her that she has finished what Klaus compelled her to do and is free to let Elena go. Isobel apologizes to Elena for being a disappointment as a mother, removes her necklace, and burns to death in the sun. Stefan and Damon realize that Bonnie is their new secret weapon since she now has tremendous power. Jeremy is upset because, if Bonnie uses too much power, she will die. Katherine, who had been set up by Isobel and taken by Maddox, wakes up to see Klaus take control of Alaric's body.