As her birthday approaches, Buffy loses her slayer powers and must do battle with a vampire who is not only extremely powerful but also quite mad.
For her upcoming 18th birthday, Buffy declines the Scooby gang's offer of a big party, hoping to celebrate with quiet reflection and a traditional trip to the ice show with her father. But Buffy doesn't know that preparations are being made for a life-threatening rite of passage that drains the slayer of her powers and then entraps her with a powerful and psychotic vampire foe.
On her 18th birthday, Buffy's dad bails out off their annual ice-show visit because of work, too late to accept a party offered by the gang. Giles reluctantly administers her under false pretenses a weakening injection, as part of a coming of age ritual, the ultimate slayer test for her and her Watcher, under instructions from the Council's visiting executive: she must be locked up in a tomb with a masterly vampire. Alas that monster, Zackary Kralik, who is permanently kept in dungeon irons, tricks his keeper Hobson while administering his daily tranquilizer and bites the man, then kidnaps Buffy's mother to enforce a duel, with a surprising victim...
- Buffy and Angel go a few rounds of fighting until Buffy pins him and holds a breadstick to his heart. They talk, and Buffy reveals her plans to go to an ice show with her father for her 18th birthday. That night in the library, Giles is quizzing her on stones and having her concentrate on staring at them. Later, while on patrol, she's nearly staked by a vampire with her own stake when her powers suddenly stop playing to her advantage.
Buffy's worried about her powers, and talks to Giles about it while trying to throw knives at a target but missing terribly. Meanwhile, Quentin Travers, the head Watcher, is setting up a "test" for the Slayer, assisted by two men named Hobson and Blair. She is to be locked in a building, without any powers, and defeat a powerful and insane vampire--Zachary Kralik. Giles meets with the head Watcher, and tries to convince him to stop the test, but it does no good. At home, Buffy is disappointed to find that her father can't come and take her to the ice show for her birthday. While she tries to get Giles to take her to the ice show, Giles has Buffy stare into a rock where she then falls into a trance. He injects her with a needle filled with muscle relaxant and adrenaline suppressors.
After Cordelia fights off an aggressive suitor who had knocked Buffy down, Buffy really begins to worry, and enlists the help of her friends to figure out what's wrong. Buffy visits Angel and he gives her a book for her birthday. She tries to sound enthusiastic about it, but losing her powers has really begun to bother her. He tells her about how he saw her before she was the Slayer and how he loved her from the second he first saw her. Kralik has the chance to break out of his strait jacket while Blair is getting his pills and water. He then turns Blair into a vampire and when he wakes up, Kralik is completely freed from his restraints.
Giles goes to find Quentin at the Sunnydale Arms building, but instead finds Kralik free and Hobson dead. Buffy, walking home alone, is first confronted by two men looking for a lap dance and then Kralik. Blair chases her until Giles drives by and picks her up. At the Summers' home, Joyce hears a noise out front and goes to check it out where she then finds Kralik wrapped up in Buffy's jacket. Giles tells Buffy that she's lost her strength due to the injections of muscle reaction he'd been giving her, and about the rite of passage. Buffy is very angry and tells him she doesn't know him anymore--that he should stay away from her or she'll kill him. Cordelia shows up and drives Buffy home, where she then finds a picture of her mother in the hands of Kralik.
Buffy goes to the Arms building, beats Blair into unconsciousness and then is chased by Kralik until his need for his pills becomes unbearable. Buffy steals them away, and slides down a laundry chute where she finds her mother tied to a chair. Kralik breaks through the door looking for his pills and water. After he downs the water, he's surprised to find out that Buffy replaced his regular water with holy water. After he explodes, Buffy tries to free her mother, then Giles shows up and stakes Blair before he can hurt anyone.
Back at the library, Quentin congratulates Buffy on her accomplishment, and then Buffy tells Quentin that he better be gone by the time she gets her powers back. Quentin tells Giles that he's fired because he's grown too close with the Slayer--his relationship with her is as more of a Father than a Watcher. He tells Buffy that a new Watcher will be assigned to her and warns Giles not to interfere before finally leaving. Buffy, grateful that Giles lost his job for her, allows him to tend her wounds. The next day, Buffy celebrates her birthday with peanut butter and jelly sandwiches and her close friends. When Buffy, minus her strength, can't open the peanut butter jar, Xander offers to help, but he can't do it either.