Phoebe and Paige have to deal with the Furies, which now includes their sister, Piper. Piper is dealing with the demon within herself.
Piper is still having a hard time dealing with the death of Prue, and getting back to a "normal life." She is on a rampage to end all evil, and to find Prue. She goes after the Furies (demons whose power feed on the emotions of others), who pick up her feelings of rage, and breathe their evil into her. Eventually this evil overtakes her, and she becomes one of the Furies. She also refuses to accept Paige as a sister, but later realizes that Paige isn't that bad and that she should give her a chance, especially since she saved her life.
By the end of the episode, she's introducing herself as Paige's sister.
Phoebe is learning to accept her new role as the middle sister, and the role of mediator between Piper and Paige. It is Phoebe who must take the forefront role when Piper becomes demonic.
Attempting to learn and accept her newfound powers, Paige visits Halliwell manor and is introduced to the Book of Shadows. She takes the Book with her (against Phoebe's direction), and uses spells on her co-workers. One of the spells, which she uses to get back at a man who is sexually harassing her, backfires, as she is using it for personal gain, increasing her own bust size. When Piper and Phoebe come to find the book, they find Paige with her new "endowments." Phoebe helps Paige get back to normal.
Paige is learning to use her orbing skills, which come in handy when the Furies come after her and Phoebe. Paige then saves Piper from remaining a Fury, and relieves her of her deep-set anger to Prue.
Leo tries to calm Piper, but even his Whitelighter skills cannot do that. Cole is very worried about Phoebe, and what Piper's rampage may do to the sisters. Cole hits Piper with a low voltage energy ball. Cole goes to the Furies, but is attacked. He then uses his old evil to call upon the Furies when Phoebe and Paige summon Piper.
Leo brings Paige and Piper (as a Fury) to Prue's grave. Paige tell Piper how much she hated her parents when they died, and that all of her anger will leave her once she tells Prue how she feels. Piper screams at Prue's grave, telling her she hates her, wants her back and how could she leave her. She then turns back into herself again.