The episode begins and Connor returns to his trailer with a head in a pillow case. The scene alternates between him talking to Professor Shane and unpacking the head, which belongs to the hybrid that was guarding him. He tells Shane he met Klaus, but he's annoyed Shane won't give him more answers. In his trailer, Connor draws hybrid venom from his severed head. Shane tells Connor not to hurt Bonnie; he needs her for his plan. When Connor won't make any promises, Shane says he'll keep her occupied. "Just do what you do, the less I know about it, the better," Shane says. Connor returns to Mystic Falls. He surprises Jeremy at the Grill, putting a knife to his throat.
Back home, Stefan resolves to find the cure for Elena no matter what it takes. Klaus calls from an excavation site in Italy to tell Stefan that Connor escaped and now has werewolf venom. With Klaus in Italy, there's no antidote. He again forbids Stefan from telling anyone what they're up to. April drops by the Grill early, telling Matt she's looking for Rebecca. Connor comes out from the back with a knife still at Jeremy's throat. Damon barges in on Elena, looking for Stefan. He realizes she didn't tell him about their dance party. Damon tries Stefan from her phone, but he doesn't answer. They think something's wrong.
Connor won't let April leave the Grill, saying they have "history." Jeremy doesn't remember talking to Connor at Klaus's and realizes he was compelled. Connor texts Stefan, Damon and Tyler informing them that, he has hostages at the Grill. Damon, Tyler, Elena and Caroline are ready to go charge into the Grill, but Stefan knowing he needs Connor alive for Klaus urges them to come up with a plan first. Sheriff Forbes has the street blocked off, calling it a gas leak. Damon wants Bonnie there, too. But Bonnie is with Shane, for "witch therapy". He's made her promise no cell phones to concentrate. He wants to try hypnosis to get her practicing magic again.
He thinks she feels guilty for what happened to her Grams and fear is the only thing holding her back. Stefan briefs Klaus, telling him to get the hybrids on board with his plan. Elena sees him on the phone. Damon studies the tunnels under the Grill from Alaric's maps. Stefan calls Elena to tell her who the hostages are. She tells Damon she wants to go in, but he thinks tipping Connor off that she's a vampire is a bad idea. Damon zips over to a nearby crossbow and trains it on her to show her she's not ready. In a flash, she leaps on him, takes it and turns it on him. In the Grill, Jeremy is still angry he was compelled. Connor shows him his werewolf toxin bomb.
Stefan rejoins them, telling them the hybrids are going to help. Elena takes note as he says again with certainty that Connor has werewolf venom, wondering how he knows. Stefan takes out a dagger and literally stabs Damon in the back, knocking him out with Vervane. Stefan tells Elena he doesn't trust Damon to keep Matt and April safe. At Tyler's house, Caroline and Hayley run into each other. Tyler and Hayley on the other hand try to talk Dean, another hybrid, out of following Klaus's direct order to attack from the front of the Grill and not fight back. Tyler tells him he doesn't have to do whatever Klaus says. He dares Tyler to prove it, over Caroline's objections, calling Klaus.
At the dig, Klaus has unearthed the sword. Tyler tells Klaus he's not sired to him anymore. Klaus is not concerned, because he threatens to tell Caroline about Tyler's time with Hayley in Appalachia. Stefan calls Connor, offering to tell him about the Brotherhood of the Five. In the pantry, Matt looks for a way out through the floor in the old wine cellar. From the tunnel, Stefan hears Matt pounding. Klaus's hybrid Dea goes in from the front as Stefan approaches from the tunnel. Jeremy tries to convince Connor that not all vampires are bad, but Connor's not buying it. The hybrid avoids the trip wire by the front door, but sets of the pressure switch explosion.
He gets covered in glass shards and Connor shoots a hole through him as Stefan comes in the pantry through the tunnel. Stefan goes to talk with Connor, who is watching his tattoo grow. Jeremy freezes in place when he realizes he's standing on a pressure switch for a bomb. Back at Alaric's, Damon wakes up and they realize Stefan took his ring. Damon puts everything together and realizes Stefan either made a deal with Klaus or he's compelled. Elena wants to go in there, but Damon warns her Connor is dangerous. "So am I!" she says. Damon is too weak, so he tells her to use the fact that Connor doesn't know she's a vampire to get close and kill him.
Back in the Grill, Elena comes in the front door and begs Connor to let Jeremy go. Connor aims at Jeremy, counting down to make Stefan come out. When Connor gets to 2, Stefan stands up. Seeing he's about to fire, Elena tackles Connor, who fires, hitting Jeremy. Jeremy bleeds profusely from his stomach, but is still stuck on the pressure switch. Stefan tackles him off it. Connor gets on top of her and is about to stake her when Stefan throws him off. When Elena stands up, Stefan and Connor are gone. As Jeremy heals from his ring, Elena asks why Connor came after him. He tells her about being able to see Connor's hunter's mark because he's like him and being compelled.
Elena is livid when she realizes who must have done it. Stefan on the other hand marches Connor through the tunnels but they run into Damon, who is ready to kill Connor no matter what. Stefan lets Connor go, telling him to run. Damon and Stefan fight but Damon pins Stefan against a wall and digs his hand into his chest, squeezing Stefan's heart until he talks. He tells Damon about Connor's mark leading to the cure for Elena. As Connor is running away through the tunnels, Elena springs on him. She chomps on his neck and tells him to stay away from her brother. He distracts her for just long enough to grab a stake from his ankle and ram it through her chest.
But she's fine. "You missed," she says as she snaps his neck, killing him. Back at college, Bonnie tries hypnosis. She thinks it isn't working, but she also didn't notice seven hours have passed. Shane takes out a candle, telling her she can light it and is stronger than the spirits. "You don't have to be afraid of anyone," he tells her. Bonnie tries to light the candle. It doesn't light, but every single other one in the office does. Alone in the woods with blood dripping down her chin, Elena furiously digs a grave for Connor. Stefan and Damon find her. She's wracked with guilt over killing someone. Tyler consoles Hayley over Dean's death. Caroline heard Klaus's side of the conversation with Tyler and thinks he cheated in the Appalachians.
Tyler explains he'd rather Klaus think that than know the truth that, he and Hayley know how to help hybrids break their bonds to him. Matt brings April back to see Jeremy, who can tell she's been compelled. Jeremy gives her his Vervane bracelet. When he looks down at his hand, he sees a hunter's mark. He doesn't tell Matt. Back home, Damon asks Stefan why he wants to cure Elena. "You want to cure her because she's a vampire and she's not cut out to be or because you can't love her if she is one?" Damon asks. "I'll always love her, but she's not supposed to be this person, I don't want her to be," Stefan says.
Damon is fine with her either way, so if he does it, he's doing it for Stefan. Elena notices blood dripping. She turns around and follows a trail of blood to her doorway and into the hall. She finds the bathroom walls covered in blood and "Killer" written on the mirror. She slips in a pool of blood but when she gets up, the bathroom is clean again. The episode ends at this point.