The gang tries, somewhat unsuccessfully, to keep the vampires at bay following Buffy's departure. Buffy, meanwhile, is living life as a waitress named Anne in Los Angeles, when she suddenly finds herself drawn through a portal and into a demonic factory which uses humans as its slave labor. After escaping and successfully bringing the rest of the humans back to Earth, she returns home to Sunnydale.
Buffy returns to Sunnydale, and amidst her ongoing battles with the undead, finds herself facing possible expulsion as well as strained relationships with both her mother and her friends.
The new slayer, Faith, arrives in Sunnydale and seems to be a typical carefree teenager, only Buffy learns that in reality, she is being stalked by a vampire who also killed her watcher.
When a student is found mauled in the woods, Oz, as the werewolf, is suspected, but Buffy fears that Angel, who she learns has returned in the form of a wild animal, may be responsible.
Feeling useless except when it comes to slaying, Buffy decides to compete against Cordelia for the title of homecoming queen. Meanwhile, the vampire Mr. Trick organizes a pack of vicious vampires and demons to take down Buffy and Faith.
Mr. Trick employs Ethan Rayne to spread around boxes of candy designed to turn the Sunnydale adults into children while he makes an infant sacrifice to the Mayor's demon.
Faith's new watcher tells of a powerful glove that a demon is searching for, which the gang must find before the demon does. With Angel's return no longer a secret, the gang tries to get Buffy to break away from him, only to realize after he rescues Willow that he has actually rid himself of the evil.
When Spike is dumped by Drusilla, he returns to Sunnydale to take vengeance on those he deems responsible, most notably Angel, and kidnap Willow so she can put a love spell on Drusilla. meanwhile, Xander and Willow briefly give in to their lingering attraction for one another and are caught by Oz and Cordelia.
When Cordelia wishes Buffy never arrived in Sunnydale, a demon grants the wish and Cordelia soon finds everything about life in Sunnydale as she knows it has been altered.
Angel, tormented by his evil past of violence, wonders if evildoing is the reason he was allowed to return from the hell dimension and is torn between returning to a life of killing, embracing happiness with Buffy, or simply burning under the sun.
When the bodies of two dead children are discovered in the park, Buffy's mom, Joyce, rallies the people of Sunnydale to track down their killers, but after Buffy, Willow, and Amy are tied to a stake in an apparent witch hunt, Giles learns that the dead childern are actually demons who feed off of people's mutual destruction of one another.
Buffy loses her slayer powers and learns that this is a routine test for all slayers on their 18th birthday, as she must face down a vampire with only her cunning as a weapon. Before the test, Buffy's vampire opponent, a former human mass-murderer, escapes and is loose in Sunnydale.
Xander goes on a mission to prove he's cool after starting to feel he is not very necessary to the gang, but when he buys a sleek car, he soon ends up as the wheelman for a gang of his own comprising the undead. Meanwhile, the gang contends with a group of demons bent on bringing about the apocalypse.
During a slayer mission under new watcher Wesley's tutelage, Buffy gets a taste firsthand of Faith's fearless methods of slaying and develops an attraction to the wild life. Faith's methods, however, become a liability when she accidentally mistakes the deputy mayor for a vampire.
Buffy confesses to Giles about the wild night that resulted in Faith accidentally killing the deputy mayor, only Faith has told him that Buffy did it. Angel tries to help reach out to Faith, but Wesley decides to transport her via boat to England during which time she makes an escape.
An alternate-universe vampire Willow creates chaos in Sunnydale. Buffy trains in hopes of outdoing Faith on the Watchers Council tests.
Faith forges an alliance with the Mayor to strip Angel of his soul, but the Mayor resorts to using a sorcerer to do the job when Faith fails to seduce Angel. Faith and Angelus then team up to capture Buffy.
Buffy decides to fight the Mayor in order to focus on her impending college plans without worry, but when she obtains a magic box which is the key to the Mayor's planned ascension, she soon must exchange it for Willow who has been captured by Faith.
Buffy tries to stop an enraged student from unleashing vicious hellhounds on the prom. Meanwhile, Xander's date, Cordelia, ends up dancing with Wesley, and Xander ends up with the demon, Anya, while Angel and Buffy share a last dance.
Anya reveals to the gang that the Mayor plans to turn himself into a demon. Faith poisons Angel, leading Buffy to face off against her in order to retrieve the cure, Faith's blood.
Faith and Buffy's massive showdown ends with Faith slipping into a coma. Buffy offers her blood to help save Angel's life, and also risks her own life in order to battle the Mayor who has transformed into a demon.
When Buffy is infected by a demon's blood, she gains the ability to hear people's thoughts which provides some use at first, but soon goes beyond her control when her mind is flooded with voices, including those of a murderer in the school.