THE VAMPIRE DIARIES Season 2 Episode 5 : Kill or Be Killedc
At the Mystic Falls picnic, Mason Lockwood tells Liz, the sheriff, that Stefan and Damon are vampires. Stefan and Damon are shot by Liz and her fellow police officers. Caroline and Elena reach the Salvatores before Liz can kill them, but Caroline's identity as a vampire is exposed to her mother. Liz rejects Caroline as her daughter, and Stefan drinks Elena's blood for strength. Caroline confesses to Elena that Katherine threatened to kill Matt if Caroline didn't spy on Elena and Stefan for her; Elena forgives Caroline. Tyler gives up the moonstone to Mason. It is revealed that Mason is working for Katherine, who wants the moonstone, and that they are lovers.