Liz accepts Caroline, and Caroline compels her mother to forget that she is a vampire. Bonnie incapacitates Mason by giving him an aneurysm. Damon then questions and tortures Mason who, believing that Katherine loves him, refuses to talk. Telling Mason that Katherine is using him, Damon eventually kills him. Bonnie has a vision of the moonstone's location in a well. Stefan discovers that the well is full of vervain , which burns him. Caroline and Bonnie help Elena rescue Stefan and retrieve the moonstone. Katherine compels Jenna to stab herself. Fearful of what else Katherine might do, Elena breaks up with Stefan for good. Needing another werewolf, Katherine compels Matt to attack Tyler, so that Tyler will kill Matt and become a werewolf.