In the gym, the cheerleaders are practicing a routine. Buffy is in the back row; she seems to have the moves down but is a little, well, agitated. After a hip-swinging move, Buffy oversteps and stomps on the head cheerleader's foot. The girl starts yelling and bitching her out. Xander and Willow (wearing a ringer T-shirt and old-man cardigan -- she used to dress like Oz!) enter the gym, and when Buffy spots them she starts jumping up and down and screaming out their names. Xander and Willow look quite apprehensive and discuss getting the "looped" Buffy out of the routine before she hurts someone. Too late for that, though, since Buffy has managed to flip the head cheerleader clear across the gym. The head cheerleader kicks Buffy off the team and appoints Amy, who is standing nearby looking haunted. Buffy begins to protest, yelling that Amy is a witch, but Xander claps his hand over her mouth and drags her out of the gym. Amy stares after them.
Out in the hall, Xander and Willow are supporting Buffy, who is staggering and babbling as if drunk. She clings to Xander, drooling that she loves him, and Xander looks quite taken with the experience, until Buffy explains that he is "totally and completely one of the girls." Xander looks stunned and Willow smirks. They continue to usher Buffy down the hall until she suddenly stops and, looking pale, slumps between their arms.
In the library, Willow is insisting that they take Buffy to a hospital, but Giles says doctors won't be able to help her. He's kneeling beside Buffy, who is reclining in a chair with a damp towel on her head. As he takes her pulse, he explains that Buffy is under the influence of a bloodstone vengeance spell. They establish that, although Amy only wanted to remove the other girls from competition, she's actually trying to kill Buffy. Giles comes clean and admits that Buffy only has a few hours to live, but that he could reverse the spell if he had Amy's spell book. Their only other alternative is to cut the witch's head off. Xander likes the sound of that plan, but Buffy defends Amy, saying she only became a witch to deal with living with her mother. They decide to search Amy's house for the area in which she casts spells, and the gang helps Buffy up. She and Giles leave, instructing Willow and Xander to stay at the school and keep an eye out for Amy.
Giles and Buffy pull up to the Madison house in Giles's little dinky car. Inside, Catherine Madison is munching on a plate of brownies, which she hides as soon as she hears a knock on the door. She runs to the door and opens it to Buffy and Giles. Catherine tries to get rid of them, but Giles forces his way inside, telling Catherine that her daughter is meddling with something very dangerous. Catherine affects no knowledge and tells them to leave, but Giles won't have any of it. As he and Catherine argue, Buffy spots the plate of brownies and starts to get a look of understanding when Catherine insists that she doesn't care about cheerleading. Buffy gently addresses Catherine as "Amy" and explains to Giles that Catherine actually switched bodies with her daughter so she could use her daughter's body to "relive her glory days." Amy confirms that Buffy is correct. Amy-as-Catherine sits on the sofa, explaining to Buffy and Giles how terrible her life was after her father left her and her mother. Her mother railed on her constantly for wasting her youth, and one morning Amy just woke up in her mother's body. Buffy, looking very limp and pale, places her hand in Amy's and assures her that everything will turn out all right.