The episode opens with the gang preparing for their graduation: Cordelia and Xander discuss the color of their gowns, and Willow speaks to Buffy about all she'll miss about high school. Buffy is considering skipping graduation to fight Mayor Wilkins, until Xander joins them and informs the two that he's to be the commencement speaker at graduation. Faith visits college professor Lester Worth on behalf of the Mayor, and kills him. She reports the kill to the Mayor, who has Faith change into a dress and tells her the ascension is her day as well as his. In class, Anya speaks to Xander, and when he mentions the ascension, and Anya's expression becomes grave.
In the library, Buffy shows Giles and Wesley the newspaper which details the murder of Worth. Buffy suspects Faith to be the culprit and the three agree the professor must have known something the Mayor wanted kept secret. Xander and Anya arrive, Anya having experienced a previous ascension. She tells them about a sorcerer who became the pure-demon Lohesh - unlike human-demon hybrids like vampires, pure-demons are much stronger and much larger. At Buffy's house, she packs a suitcase for Joyce and convinces her to leave town for safety. At Willow's house, Willow complains about chaos the ascension would mean and yells at Oz for his detachment from the situation. Oz interrupts her with a passionate kiss, and when Willow asks what he's doing, he replies that he is "panicking". The two finally consummate their relationship.
Buffy and Angel discuss Worth's work, which Buffy doesn't understand. The two discuss the confusing nature of their relationship, when Angel is struck in the back by a crossbow arrow from Faith. At the library, the arrow is removed, and Giles and Wesley go over Mr. Worth's files, which indicate that Worth found a gigantic carcass underneath the rubble of a volcanic eruption, which he believed may have been a new type of dinosaur. The group assumes this must be some sort of demon, when Angel falls to the ground - the arrow has been poisoned with a toxin fatal to vampires. Faith reports her attack to the Mayor, and amuses him with a few stories from her childhood before he continues preparations for the ascension. Wesley tells Buffy the Watcher's Council refuses to help Angel because he is a vampire, but Willow's research reveals the poison has a cure - the blood of a Slayer.
Buffy arrives at Faith's apartment, and the two battle, eventually taking the fight to the roof. Meanwhile, Giles and Xander find that the Mayor will transform into the demon Olvikan, and find an unseen picture of him in a book - the illustration is four pages long. The Mayor is also alerted to the trouble at Faith's place. On the edge of the roof, Buffy stabs Faith with the knife Faith had received from the Mayor, and Faith congratulates Buffy for killing her, then leaps off the roof onto a truck on the street below. The fall knocks her out, and Buffy watches as the truck carries her away.