Elena tries dragging Stefan off to school but he just wants to make out. She goes downstairs and Damon jumps her, assuming she's Katherine. Elena's confused but soon starts to realize Katherine isn't in the tomb. Stefan runs upstairs and grabs Elena, threatening her until Katherine actually walks in and clarifies things. They go downstairs and Katherine explains that they need her to fight Klaus. Damon goes down to the crypt to try and burn what's left of Elijah. Katherine strolls in and starts prodding him. He threatens her with him flamethrower and she reminds him they are after the same thing.
Stefan and Elena head to school and try to figure out why Katherine is sticking around. They go inside and join Jeremy to fill Bonnie in. Stefan wants to get the Martins on their side and asks the witch to help. Once the vampire and Elena leave, Bonnie promises Jeremy she will tell his sister about them soon. Down the hall, Alaric tells Elena that he can't keep secrets from Jenna anymore. She wants to hold off on revealing the truth until they've dealt with Klaus.
The Martins arrive at The Grill to meet Stefan and Bonnie. They explain that Elijah is dead and suggest they all work together to get Luka's sister back. The Martins don't like this and leave. Luka's dad refuses to trust the vampires and suggests they just let Elijah kill them. They get out their spell books and candles to cast a spell. Back at home, Damon goes upstairs to pout and flip through the Gilbert journals. Katherine tells him about the witch massacres and Stefan arrives to say he knows more. They sit around and read when Luka's invisible body magically appears and starts looking around. Katherine goes down to grab some blood while the brothers spot something in the books. In the crypt, Katherine notices the dagger magically coming out of Elijah. She pushes it back in and Dr. Martin orders his son to drive a stake through her heart. She calls out as one flies into her guts. Damon grabs his flamethrower and starts spraying the room. Luka starts to burn. Dr. Martin tries casting a spell to save his son but Luka is burnt to death. In a rage, Martin whips out a picture of Elena and casts a spell. Stefan breaks in and the warlock tells him he's about to find out what it's like to have no one.
At school, Caroline tries chatting with Matt but he's worried about Tyler. She starts mumbling. He reminds her that she knows how he feels so she needs to make a decision. Later, she goes off to meet Bonnie and Elena for girls' night. Jenna shows up and they offer to listen to her if she needs to talk about Ric. Caroline decides they should all go dancing at The Grill. When they get there, things get awkward when they see Ric and Matt. Jenna tries avoiding Ric but he wants to talk. She tells him she can handle anything and doesn't need him keeping things from her. When the band ends a song, Caroline runs up on stage and starts babbling about how she doesn't know how to express herself. The band want to kick her off but she uses her vamp power to make them play back up. She belts out a song for Matt, who rushes the stage and kisses her. The audience claps. The couple slips into the bathroom to make out and Bonnie asks Elena if it would freak her out if she started dating her brother. "He deserves to be with someone as amazing as you," Elena says.
At home, Damon jabs Katherine with a stake for not telling him the dagger would kill him. He threatens to put it in her heart next time. She tells him she made a deal to protect them, but she could only save one of them and she picked Stefan. He hears that Luka is dead and guesses what that means. She insists on going with him when he wants to go after Dr. Martin.
Dr. Martin storms into The Grill looking for Elena. Bonnie tries to stop him. He blows out all the lights and knocks Bonnie out. Stefan shows up and Elena tries reasoning with Martin. Caroline jumps him and he throws a spell at her. Matt tries to jump him and Martin jabs a smashed bottle into his neck. Seeing him bleeding to death, Caroline bites herself and makes him drink. She takes him home and he wakes up later. "I'm a vampire," she confesses. He starts to freak out and demands to know what she did to his sister.
Bonnie and Jeremy go back to his place and she beats herself up about what's happened. Elena and Stefan arrive. She goes upstairs and Dr. Martin lurches out to grab her. It's actually Katherine though and she promptly kills him. When Bonnie crouches down to see him, he leaps up and grabs her head until Katherine kicks him back down. They go downstairs. Elena isn't happy that Katherine's there. Katherine reminds her that she isn't a threat as long as Klaus is alive. Upstairs, Jeremy tells Bonnie he'll be there for her. She kisses him and explains that when Martin grabbed her, he gave her powers back so she can kill Klaus. Outside, Alaric walks Jenna home and tells her that he loves her, but there are things about Isabelle's death he can't tell her. "Good night," she says. She goes in and eats ice cream with Elena until Isabelle suddenly shows up at the door. Meanwhile, Katherine tells Damon that he was very mean to her today. She tries to make out with him but he pushes her away.
Cryptic commentary: More dead characters and my poor Elijah was stuck rotting away for the whole episode. At least Katherine was back in the mix and as amusing as usual. Having Isabelle pop up at the end like that was a nice touch. But what was really good this week was Caroline finally coming out as a vampire to Matt. I just wish they'd been given more time.