Buffy leaves Faith's apartment after their battle, and the Mayor appears inside the broken window overlooking the roof and orders his minions to find Buffy and Faith. Xander and Giles are in the library, and Cordelia enters and demands to know what happened to Wesley, who is upset and leaving the country. Giles informs Cordy that Buffy has quit the council and no longer requires a watcher. Willow and Oz are watching over Angel, when Buffy arrives and sends them away. With Angel near death, Buffy hits him until he shows his fangs, and forces him to drink her blood to cure himself. Angel rushes Buffy to the hospital, where she is saved. In a nearby room, another doctor is informing the Mayor that Faith is in a coma. The Mayor overhears nurses talking about Buffy, and attempts to suffocate her before he is stopped by Angel and leaves.
In a dream, Buffy and Faith have an exchange in Faith's apartment. The two trade cryptic comments, and Faith assures Buffy she'll heal. She also tells Buffy that "human weakness never fades, even his". The two clasp hands, and Buffy awakens and approaches her friends, ready to go to war with the Mayor. In the library, Buffy finishes detailing a plan (which the audience does not hear), and the gang agree the plan is crazy, but is their only option. Giles cautions that the plan is entirely contingent upon Buffy's ability to control the Mayor. Buffy explains what Faith had told her about human weakness, and Angel remembers that the Mayor was seriously grieving over Faith. Wesley arrives and says he is there to help of his own volition, not on behalf of the council. The Mayor and Buffy detail their respective plans to their allies, and Buffy's friends recruit other students to help. Wesley tells Cordelia that he will be returning to England following the ascension, saying he has no reason to stay now that Buffy has fired the council.
Buffy and Angel talk over weapons, and Angel tells Buffy he won't be saying good-bye after the battle. A grief stricken Buffy unwraps the knife she used to stab Faith, still stained with her blood. The graduation ceremony begins and Principal Snyder welcomes the students before the Mayor takes the podium. The Mayor tells the students that it is the 100th anniversary of the founding of Sunnydale, and during the rest of his speech suddenly convulses. An eclipse begins, and the Mayor decides to skip the ending to his speech, and transforms into Olvikan, a giant snake-like demon. Everyone but the students scramble to flee, when Buffy yells "NOW!", and the entire student body removes their robes to reveal weapons and crosses, ready to fight. Xander and Angel lead the students into battle against the Mayor's vampires, and in the chaos the Mayor devours Snyder as he rages at him.
Buffy catches the Mayor's attention with Faith's knife, describing in graphic detail how she stabbed her. The Mayor chases Buffy through the school to the library, where all of the books have been removed and the room filled with explosives. Buffy dives out a window as the Mayor exclaims "well gosh!" Giles detonates the explosives, blowing up the school and killing the Mayor. EMTs and firefighters are now at the school helping the wounded, and Buffy is looking for Angel. Giles presents her with her diploma, rescued from the debris. He leaves and Buffy then sees Angel, and starts towards him, but he turns and walks away. The gang, minus Giles, gathers and Willow asks if she is okay, and Buffy says she is. Oz tells them all to take a moment to deal with what happened, that they all survived. Buffy agrees that it was a great battle, but Oz corrects her by saying they survived high school. The scene fades on a charred yearbook for Sunnydale Class of 1999.