Dawn helps Willow move into her new room at the Summer's house while giving her advice on how to fit in with people at school. Buffy and Xander contribute to the effort as well while talking about Anya. Buffy wonders about Anya's evil intentions, but Xander thinks she's getting better and isn't a threat. At a frat house, dead male bodies litter the room, each one with his hearts ripped out. Anya sits on the floor, covered in blood and in completely shock by the violence she's caused. In Sjornjost, 880, a pre-demon Anya, then named Aud, cares for her Viking husband Olaf after he returns home from a hard day of fighting trolls. She feeds him, but worries about whether he's been faithful to her.
In the school basement, Spike talks to Buffy about his mental struggles and Drusilla. Buffy is kind and reassuring that she'll help him get through his struggles. Then the real Buffy comes downstairs and tells a tearful Spike to get out of the basement and away from whatever is making him so crazy down there. Willow talks with one of her professors about returning to class and then she runs into Anya leaving one of the fraternity houses wearing a trench coat. Anya's very distant and claims she's dating one of the frat boys before quickly rushing off. Willow spots a streak of blood on Anya wrist before she runs off and goes to investigate the building.
Willow finds the frat house covered in blood and a young woman cowering and crying in the closet. The woman explains how she wished the fraternity boys could have their hearts ripped out after her heart was broken by one of the boys. She didn't intend for it to really happen, but then a giant spider showed up and ripped out the hearts of all the boys in the house. Willow uses dark magic to hold the spider at bay and loses control for a minute, snapping at the cowering woman before tossing the spider through a window and apologizing for her outburst. Back in Sjornjost, 880, as a newly turned troll, Olaf runs from a mob of villagers who intend to kill him. Aud watches the proceedings along with D'Hoffryn who appreciates her fine magic. She turned him into a troll after he cheated on her with a barmaid. D'Hoffryn convinces Aud that she should go into the vengeance business and that her true destiny is as Anyanka, Vengeance Demon.
At work, Buffy receives a call from Willow about the frat house and the spider demon. Meanwhile, Halfrek praises Anya violent vengeance while Anya expresses her difficulty to deal with the effect the act has had on her. Willow barges into Anya's place and orders Halfrek out. She tries to offer help, but Anya isn't in assistance, especially from Willow. Buffy and Xander search through the woods outside the frat house for the spider and find another dead body. The spider attacks them and nearly kills Buffy, but she manages to throw it off and kill it with an ax.
Buffy and Xander return to the house and find Willow waiting with an explanation about where the demon originated and the damage it caused. Xander blows up at Willow because she didn't tell them, but she did it because Buffy would feel obligated to kill Anya as a result. In St. Petersburg, 1805, Anyanka and Halfrek dine on champagne after massacring a room full of men. Anyanka is set in her ways and focused on Vengeance. Buffy is determined to kill Anya because of the violence she's caused. Xander can't believe she would kill Anya and desperately tries to convince Buffy to change her mind. They argue about their actions with Spike and Willow and Buffy reminds Xander that she killed Angel in spite of her love for him. Buffy thinks Xander's love for Anya is clouding his judgment and encourages him to find another alternative, although she doesn't believe one exists. Xander rushes out to find a way to prevent Anya's death while Buffy sets out to cause it.
Left on her own, Willow rushes to her room and finds the talisman D'Hoffryn gave her years ago and she summons him. Xander finds Anya at the fraternity house and tries to offer help and warning of Buffy's intentions, but again Anya isn't interested in his assistance. Buffy shows up and after Anya turns into Anyanka and knocks Xander out of the way, the girls break out in a fight. The struggle and toss each other around for a while, but armed with a sword, Buffy as a mild advantage and manages to stab Anya in the chest. In a flashback to 2001 when Sunnydale residents were consumed by the desire to sing, Xander sleeps in recliner while Anya breaks out into song about her relationship, life as a human, and her upcoming marriage to him.
In the present, Anya wakes up from her stabbing induced unconsciousness and rips the sword out. The fight continues and Xander intervenes when Buffy raises the sword to stab Anya again and D'Hoffryn pops in, interrupting the rest of the battle. He examines the viewpoints of all the Scooby Gang in regards to Anya's future, but wonders what Anya wants to do. She asks to take back her vengeance and because of the enormity of the act, a Vengeance demon must die in exchange for the reversal. Anya accepts the steep price and is prepared to die to undo what she's done. Instead though, D'Hoffryn makes Halfrek appear and die in Anya's place as a punishment to her. With a parting threat about the big evil, D'Hoffryn departs. Hurt and scared, Anya walks out alone, but Xander follows. She expresses her worries about surviving on her own and whether she actually has a role in the world. He offers some comforting words, but her problems and fears require time to be repaired. Xander walks off into the night while tearfully, Anya moves in the opposite direction, facing the future on her own.
