Jenna is brought home. Elena tells her brother that they aren't going to go after Katherine; they're going to do what she says for once. He heads out. Over at the Salvatore's, Caroline tells the brothers that she was stalking Matt when Katherine cornered her in the bathroom. She demanded that the brothers give her the moonstone or she will kill more people. Damon decides that he is going to this over with and kill Katherine at the ball. Stefan wants to kill her first. Alaric and Jeremy arrive and Bonnie shows up as they begin sorting out their weapons. Bonnie's reluctant but agrees to go along with this as long as Katherine is the only one to get hurt.
Katherine and Lucy get ready for the ball and talk about the moonstone. Lucy guesses she wants the stone to break the curse. Over at the Lockwood's, Tyler and his mom get ready for the ball. He apologizes for being a dick and they talk about his father. The guests are filling up the house. Matt is there, but he's not sure why. Katherine arrives disguised as Elena and corners him, giving him orders to start a fight with Tyler and get himself killed.
At home, Jenna tells Elena that Jeremy has gone to the party. She suspects something is up. When Alaric tells her that Stefan is at the party too, she's sure of it. Meanwhile, the brothers arrive and take everything in. Jeremy and Bonnie sneak upstairs and start to prepare their weapons. She flips through her spell book. Outside, Katherine pulls Stefan into a dance and begins taunting him about the moonstone. Amy wanders by to tell 'Elena' how good she looks. Katherine promptly kills her and chucks her limp body at Stefan, demanding the stone before sashaying away. Stefan runs off to his brother with cold feet but Damon demands that they end things tonight. Across the field, Lucy is miffed to realize that there is another witch there. Katherine fobs her off as Jeremy walks over and tells her that the vampire brothers want to meet her by the water. He walks off to the woods with Bonnie and grabs his sister as she arrives, explaining everything to her.
Caroline arrives and spots Matt. He look away and walks off with Tyler. As she goes for the bathroom. Katherine grabs her by the throat and demands to know what's up. Caroline tells her everything. They go upstairs and Stefan is waiting with a stake in his hand. "You don't think you can kill me with that?" she sneers. Damon walks in and shoots her in the back. Simultaneously, Elena spasms in pain and begins to bleed. Bonnie sends Jeremy to stop the killing. Katherine beats the crap out of the brothers. Just as they get her on the floor to finish her off, Jeremy runs in and tells them to stop. After he explains what's happening, Katherine says that her witch is better than their witch and starts torturing herself to hurt Elena. Damon and Katherine bicker about the moonstone. She taunts them and Stefan starts to wonder why she's so interested in werewolves. As he probes, she gets flirty. Damon tries to kill her again but his brother stops him.
Back in the house, Tyler and Matt are getting drunk. Matt begins pouring booze on a picture of Tyler's dad and then they throw each other around. Caroline runs in and breaks them up. After she knocks Matt out, Sarah gets zombified and attacks Tyler with a letter opener. He pushes her to the ground. She's dead. He wretches and screams. Later, Caroline calls Carol in and gives her a story about what happened. She leaves to call the sheriff. Tyler wonders why Caroline is covering for his mistakes. He's shocked to notice that his wound has healed. Meanwhile, Bonnie runs into Lucy and tells her to stop the spell. When Bonnie gets pushy, Lucy senses she has the moonstone and demands it. Moments later she's upstairs handing it to Katherine. Once she has it, Katherine starts to choke and collapses. Lucy says the spell is broken and apologizes to everyone.
Outside, the witches talk and realize that they are cousins. Lucy is tired of letting vampires control her and thanks her for the wake-up call. Bonnie wants to stay out of the fights too, but Lucy tells her that she's good and needs to stay in the middle of things. Jeremy walks out and offers her a ride home. Meanwhile, Stefan finds Elena in the field and confirms that Katherine is gone. She tells him that she wants to be with him, but she can't do that until she feels safe. As she heads home, a man in a mask grabs her. Down in the crypt, Katherine wakes up and Damon comes out of the dark to tell her death would have been too kind. She claims that Elena is in danger. He doesn't believe her and seals her in.
Cryptic commentary: Bonnie and Jeremy are getting close fast. It was good to see her growing a lot in this episode and interacting with another witch. Caroline and Tyler definitely have some chemistry and could become an intriguing pair. Again, a lot of action. Maybe too much is such a short space. Who could have grabbed Elena? Could this have something to do with the vampires on the way?