In Florida a year ago, Mason got in a fight with some drunken dude over a chick and accidentally split his head open. Mason explains this to Tyler and how this killing triggered the werewolf curse. He warns him that even an accidental death could cause a lifetime of dealing with this.
Elena tells her brother to stay away from the Lockwoods. Stefan suddenly pops up and they discuss the fake fighting they need to do for Katherine's sake. He goes to find Mason and offers him a truce. Mason already made that offer to his brother and got knifed for it. When Stefan warns him that he better watch his back since there are two of them, they shake on peace. As soon as Mason's gone, Damon pops up and the brothers bicker. Meanwhile, Mason wants to talk about the Founding Fathers and tells Liz that the Salvatore brothers are vampires. She refuses to believe that so he offers to prove it.
Caroline is startled when her mom offers to spend the whole day with her. When her mom digs for what has been bothering her, Caroline frowns walks away. She finds Elena and complains about her mom. Elena gives her the spiel about breaking up with Stefan. She spots him so goes over to fight with him in front of everyone. Caroline and Damon listen in. He later teases his brother about it. When he takes a swig of lemonade a kid hands him, he spits it out and begins choking. He's sure Mason was trying to poison him. Liz glances over. Meanwhile, Elena mopes by the water with Caroline. The blond notices her mom running off and chases her down. Liz apologizes and heads off. Caroline uses her superlistening as Stefan and Damon corner Mason in the woods. Liz and some cops leap out and shoot the vampires, grabbing a sample of their blood. They dump them in the old slave quarters. She sends Mason away so she can finish them off. He finds the girls outside. When he threatens to crack Elena's neck. Caroline pounds on him and throws him at a tree. Underground, Liz continues shooting the brothers and demanding answers. Elena runs in to stop them. Caroline races past her and kills the cops but stops short at Liz. "Hi mom," she says. Damon refuels on the cops. Liz stares. She'd rather be dead than have a vampire for a daughter. Damon decides not to kill Liz. She declares that her daughter is dead to her. Caroline runs off.
At his place, Stefan searches around and stares at his blood supply. He tells Elena that he needs to build up a tolerance to it so he can keep up his strength and protect her. She goes upstairs. Caroline cries and tells her that she is afraid to go home and see Katherine. She confesses that she's been working for her. After tucking Caroline in for sleep, Elena goes for the door. She runs into Damon and thanks him for not killing Liz; he seems more like her old friend again. He tells her that she knows his brother needs to start drinking blood again. She goes to Stefan and says he should go for it, but she doesn't want him to do it alone. "It's you and me," she says, cutting open her hand and letting him drink. They kiss.
Sara, Jeremy, Tyler and Amy hang out at his place. They find some sketches of werewolves. Tyler takes Jeremy into the office and roughs him up. Jeremy admits that he knows what he is. Tyler says that he's not a werewolf yet and shows him the moonstone. The women come in and grab the stone away. Sara runs upstairs with it to lure Jeremy after her. Tyler tries to get the stone from her and she falls down the stairs. For a second they think she's dead. Tyler goes to see Mason and tells him what just happened. He admits that for a split second, he wanted the girl to die and he never wants to feel that again. He hands him the moonstone. When he goes out to his car, Katherine is waiting for him. She's not happy about what happened today. She is happy when he tells her he got the stone though.
Cryptic commentary: Another action packed episode. Is it just me or was there something strangely humorous about watching Liz trying to kill Damon? Poor Caroline. Her whole life is turning to crap right now. Having Katherine leap in at the end like that ended things on a really crisp note.