The scene opens with Damon getting a call from Katherine. She knows where Klaus and Stefan are. She tells Damon that Klaus' hybrids didn't work. Stefan and Klaus arrive in Chicago. Flash back to the middle of Prohibition, Stefan draining a young woman in the backseat of a car. He goes into a speakeasy where a woman named Gloria is singing. Stefan eyes a hot blonde who knows who he is. She kisses him and approves of the blood on his lips, a fellow vampire. Back in the present, Klaus announces they're going to see his favorite witch for help with his hybrid problem. Elena wakes up in bed to find Damon next to her. He tells her Stefan's in Chicago. In the dungeon, Caroline calls for her dad Bill. A mist comes in and makes her choke. He comes in and tells her he's sorry "this happened to her." He wants to know how they walk in the sunlight. She points to her ring. He takes it off. He tells her the dungeon where he's holding her used to be used on vampires. Vervane in the ventilation reinforced steel chair and a window with steel blinds.
He taunts her with a bag of blood, saying its how he's going to fix her. He opens the window blinds, burning her with sunlight. On the road, Damon gives Elena Stefan's diary. She refuses to read his private thoughts and thinks she's already seen him at his darkest and can handle it. Damon drives and reads. Stefan writes he wakes up covered in stranger's blood with strange women. Elena reads. Back in the speakeasy, the hot blonde, who's a Brit, shushes Stefan and his friends so she can hear the singer. In the present, Stefan and Klaus return to the speakeasy, where they find Gloria, who is older, but not dead. She's a very powerful witch. Klaus sends Stefan away. He listens to them talk. Gloria says to find out what went wrong with the curse they'd have to contact the witch who made the spell, who is very dead. She'll need help to contact her. "Bring me Rebecca," Gloria says. Stefan finds a photo behind the bar. It's him with Klaus, but he has no memory of it. Back in Mystic Falls, Tyler goes to see Sheriff Forbes to talk about Caroline who may be in trouble.
At the same time, Caroline screams in pain as her dad repeatedly burns her with sunlight. She swears she doesn't hurt anyone. He says if she could handle it, she wouldn't react to the bag of blood. He shows it to her again. She fangs out. He's trying to condition her to associate vampirism with pain, so she'll learn to repress it. She tells him he can't change who she is. He burns her some more. Damon and Elena visit Stefan's old Chicago apartment. Damon goes to the secret closet, which looks like it's full of moonshine. Elena sees the list of names. There are hundreds. Damon says Stefan was a "cocky ripper douche" back then. He kept his distance. He leaves her to go look for Stefan, telling her to come up with a plan. At the speakeasy, Stefan is upset he doesn't remember he knew Klaus. Klaus says they didn't get along. Flash back to Stefan and the blonde sharing a woman again, drinking from opposite sides of her neck. The two vampires start making out. She has an old necklace; the same one Elena wears in the present. She says it was from a witch.
They're interrupted by Klaus, her brother, who's going by "Nick." In the present, Stefan processes he knew another original vampire. In a warehouse, Klaus opens up a coffin. There’s his sister, Rebecca, preserved with a dagger through her chest. Stefan doesn't remember her. Klaus warns she has a worse temper than him. He removes the dagger. In another flash back, Klaus quizzes Stefan on why he's worthy of his sister, an original. Klaus killed most of his family, but not Rebecca, after she chose his side. They're interrupted by a man demanding to see his wife. Stefan calls over one of the dancers then compels him to stay put as he slices her wrist and lets the blood drip into a glass. He asks the man's name, and then tells the man, Liam Grant, to drink. In the present, Klaus tells Stefan he was his biggest fan. Klaus compels the warehouse security guard to direct Rebecca to Gloria's, and then let her feed on him till he dies. Klaus tells Stefan he entrusted him with one of his biggest secrets and he's going to prove it.
They're going to his old apartment. Damon pays Gloria a visit. She says Damon's with Klaus and will be back in later tonight after they run an errand for her. She won't tell him what. Elena reads Stefan's journal, about Lexi detoxing him. Elena hears Klaus and Stefan coming. In the hall, they see the door busted in. Elena hides in the secret compartment. Klaus tells Stefan he asked for Liam Grant's name then told him his secret, part of his ritual. In the small room, Elena sees Liam Grant's name on the wall. Stefan remembers he wrote down the names to relive the kill, over and over again. Klaus opens the secret door and holds it open for Stefan to walk inside. Elena has nowhere to hide, but is around the corner where Klaus can't see her. Stefan looks right at her, then announces to Klaus: "Look what I found." He grabs a bottle of single malt Scotch and off they go. Damon returns with clothes for Elena. She called him an hour ago. He says he had that long to process what a bad idea it was to leave her alone and move on. He checks she's OK. He knows where they'll be later, but wants to make sure she can deal with Stefan while he distracts Klaus, because he won't have long before Klaus rips his heart out.
Klaus and Stefan return to Gloria's. Klaus says Stefan used to want to be his wingman. Flashback to Stefan telling Klaus he's a king. They drink up at the bar. Klaus warns Stefan about his sister and not to do anything stupid when she leaves him. Back in the dungeon, Caroline is exhausted from being scorched. She tells her dad she doesn't need to be fixed. He puts the blood in front of her again and makes her fight the urge. She tells him she's starving. He says he has to fix her so he doesn't have to kill her. The sun has gone down; he promises to try again tomorrow. He leaves and locks the door behind him. He looks up to see Liz pointing a gun in his face. Caroline hears Bill plead with Liz to let him proceed because they love her. Liz calls for Tyler. She fires a warning shot at Bill when he resists. Tyler goes in and releases Caroline, putting her ring back on her. He carries her out of the dungeon.
Stefan and Klaus drink up at Gloria's. Flashback to Stefan dancing with Rebecca, when suddenly Klaus' senses tingle. The police bust in and start shooting the place up. Stefan and Rebecca hide behind the bar and she sees they're using wooden bullets. "That means he's here," she says and they run. She drops her necklace on the way out. Klaus compels Stefan to forget he ever knew them, until he says otherwise; thanking him for reminding him what it was like to have a brother. In the present, Stefan asks who Klaus was running from. Damon comes in and signals Stefan, who excuses himself. Outside, Stefan tells Damon that Gloria is seconds away from figuring out the doppelganger isn't dead and that's why he can't make hybrids. It's too late to send Elena home, she's at the speakeasy. Damon sits down with Klaus. Klaus promised Stefan he wouldn't kill Damon. Klaus wonders how long he has to honor that. Outside, Elena hugs Stefan and asks him to come home. We see she has a syringe in her hand and is about to stab it into his back. But he catches her and knocks it away, asking how many times he has to tell her he doesn't want to come home.
Inside, Klaus has lifted Damon off the floor by his neck and is stabbing him with a cocktail umbrella. Damon offers himself as a partner in crime instead of Stefan. Klaus throws him across the room and is about to stake him when Gloria ignites the stake and tells him to take it outside. Klaus promises when he's done with Stefan, he won't want to come back. Outside, Stefan explains as soon as Klaus figures out she's alive, he'll know why he hasn't been able to make hybrids. He says if he goes with her it won't be the same, he's killed innocent people. He says it took him 20 years to pull himself together the first time. She doesn't have that long to wait. He says it's done. "I don't want to see you, I don't want to be with you, I just want you to go," he says and walks away. Damon rejoins Elena in the car. She just wants to leave. Liz feeds Caroline bags of blood in bed back home. Liz tries to explain her dad has long held beliefs. He'll come around. Tyler asks if now would be a bad time to give her crap for sneaking out on him.
He climbs into bed with her and holds onto her. Klaus returns to the warehouse to find his sister's coffin empty and the guard drained. Suddenly she's on him in a flash, and stakes him through the chest, calling him Nick and telling him to go to hell. Flash back to the 1920s, Klaus telling Rebecca they have to go or they'll be caught. She says she doesn't want to run anymore, she wants to be with Stefan. He tells her to choose between him and Stefan. She says goodbye. He stakes her. In the present, Klaus calmly removes the knife from his chest, unhurt. He forgives her, saying he understands she's upset. Klaus calls in Stefan, and then tells him he can remember. All of Stefan's memories of Rebecca come back, and of Klaus.
Klaus tells Rebecca that Gloria needs something from her. She realizes her necklace is gone. Damon talks to Katherine in a phone booth again, saying she was right about Chicago. She won't tell him where she is now. Flash back again, to police busting into the speakeasy. Katherine is there and sees the necklace. Stefan picks it up. A man shows him sketches of Klaus and Rebecca. Stefan says he doesn't know them. Katherine leaves her phone booth. We see she's in Chicago. The episode ends.