Summer vacation is nearly over, and Buffy is still missing. Giles is searching for her. Her friends are carrying out her patrols for her, but are staking only about half the vampires. Meanwhile Buffy, going by her middle name of Anne, is a waitress in a diner. She just wants to be left alone, but Lily, a customer, recognises her. Buffy had once saved her and her vampire-wannabe friends from the real vampires. Then Lily's boyfriend Ricky disappears, and Lily asks Buffy for help. Buffy, still very depressed, doesn't want to, but reluctantly agrees. Buffy finds a very old dead man, yet recognises him as Ricky. Then they are both captured by a devil-creature, who is abducting street kids and taking them into a subterranean slave hell, where time runs faster. Buffy finally snaps out of her gloom, beats up all the bad guys, and rescues the slaves. Realising she cannot deny her responsibilities any longer, she goes home.
Buffy's back, but all the old relationships are very strained, and she's still expelled (if no longer wanted for murder). But her mother has an old Nigerian mask on the wall, which is reanimating the dead. A very uncomfortable welcome home party for Buffy degenerates into a slanging match, when it is interrupted by a bunch of Zombies after the mask. A big fight breaks out, the zombies are defeated, and a lot of the tension has dissolved. Giles threatens Principal Snyder in order to get Buffy reinstated.
The school board overrule Principal Snyder, to let Buffy back in school. Buffy is still having nightmares about Angel, and hasn't yet told anyone what really happened. Faith the Vampire Slayer, Kendra's replacement, turns up -- she's very bright and popular, but seems to take a lot of pleasure in beating up the vampires before she stakes them. Buffy's mother learns that Buffy died at one point. Mr Trick and another, very old vampire, turn up -- they killed Faith's Watcher, and are now after her, and it's up to Buffy and Faith together to destroy them. Buffy, trying to make a new life after Angel, puts away his ring -- and this somehow makes him reappear.
Someone has been eaten in the woods -- and Oz may have been responsible. While Willow seeks evidence in the morgue to clear Oz, Buffy sees Angel, reverted to an animal-like state after his subjective hundreds of years in hell, and worries it might have be him. She catches him, and chains him up, and doesn't tell anyone she has seen him. But then the school councillor is killed in broad daylight, minutes before Buffy turns up for her mandatory session. So both Oz and Angel are in the clear. The real killer is yet another student, doing a Jekyll-and-Hyde act to keep his girlfriend. Oz is in the clear, and Angel reawakens to the real world.
Mr Trick is rounding up hunters, human and demon, for the ultimate "slayerfest", with Buffy and Faith as the prey. It's Homecoming Queen time, and Cordelia is getting obnoxious, so Buffy decides to run as well. This puts all their friends in a difficult position, especially when Buffy and Cordelia have a big fight. So they decide on a plan -- they leave the two together to sort out their difference in the limo ride to the prom. Unfortunately, the hunters don't know of the change in plan -- the limo is hijacked with everyone thinking it contains Buffy and Faith. The hunt is on! After lots of slaying, the duo end up back in the library, only to be met by an unconscious Giles, and two vampires. Buffy kills one vampire, but is knocked out -- leaving Cordelia to the mercy of the other. But, in her finest hour, she pretends to be Faith, and bluffs him into running. Buffy and Cordelia turn up for the Prom rather the worse for wear, to discover neither has won the competition. Mr Trick is hired by the Mayor.
The Mayor needs to make an offering to one of his demons, so engages the help of Mr Trick. Strange candy starts making all who eat it behave like teenagers. Giles reverts to his tough Ripper personality. He and Joyce make out. Buffy, freaked by the weird irresponsible behaviour of her mother and the teachers, discovers that the candy is the problem, and goes to the candy factory, where she discovers it is all a ruse to get the hospital unguarded, so that babies can be stolen for the demon offering. She saves the babies and roasts the demon, then goes back to school to sit her SATs.
A new Watcher arrives to take charge of Faith, and brings warning of a Demon seeking a Glove of power. Angel finds the glove, but Xander spots him leaving a cemetry and follows him, where he sees him in a clinch with Buffy. Now her secret is out, and all her friends feel betrayed. Faith goes off the slay Angel. Meanwhile, the new Watcher has discovered from Giles that Angel has the glove, and goes to retrieve it. Buffy stops Faith slaying Angel, and they fight. But then the Watcher dons the glove -- she is a renegade, after its power. Buffy manages to kill her, but Faith now feels betrayed by everyone.
Willow tries to find a spell to quell her passion for Xander. A lachrymose Spike is back, grief stricken because Dru has dumped him. He kidnaps Willow and Xander, to force Willow to make a love spell for him. Buffy and Angel capture Spike at Buffy's house, and try to force him to tell them where their friends are. Spike tells Buffy and Angel that they are obviously still in love. On their way, a group of vampires ambush them, and in the fight, Spike comes back to himself, and dashes off to torture Dru until she loves him again. Meanwhile Cordelia and Oz find Willow and Xander, but discover them kissing. Cordelia runs away, and is badly injured in a fall. Buffy splits up with Angel. In the end, no-one is talking to anyone, and Spike is the only one happy, driving back to Dru.
Xander and Willow are each desperately trying to make up with Cordelia and Oz. Cordelia is back at school, mostly recovered from her injury, but being laughed at by all for being cheated on by Xander. Her only friend is a new girl, who gives her a good luck locket. When Cordelia wishes that Buffy had never come to Sunnydale, it is granted -- the locket grants wishes to women scorned. But the new world is grim -- demons and vampires control Sunnydale -- Willow and Xander are the Master's chief vampires. Cordelia, who remembers the old world, contacts Giles, and tells him to get Buffy, before herself being killed by Willow and Xander. Giles finds the locket, and realises it is the key. Buffy the loner arrives, and goes off to the Master's factory to kill him. In the ensuing fight, everyone dies: Xander kills Angel, then is killed by Buffy. Oz kills Willow. Then the Master breaks Buffy's neck. But at that instant, Giles destroys the locket's power -- and the old world is restored. No-one remembers what happened.
It is Christmas. Oz misses Willow so much, he's willing to give the relationship a second try. Cordelia is not as forgiving to Xander. Meanwhile, Angel is having a series of dreams about his former victims, who then start haunting him in real life. He begs a very unsympathetic Giles for help. Actually, his problem is an Old Evil, trying to get him to kill Buffy. He refuses, and chooses to die instead, by letting the sun rise on him. Buffy, who has been sharing some of his dreams, discovers his plan, and desperately tries to dissuade him. He won't be turned, but then it miraculously starts to snow, and the sun is hidden all day.
Joyce Summers finds two dead children with a strange symbol on their hands. Deeply upset, she starts MOO -- Mothers Opposed to the Occult. But the movement quickly develops into a true witch-hunt -- witches are harassed, Giles' books are confiscated, and ultimately Buffy, Willow and Amy are about to be burnt at the stake by their respective parents, for their own good. Amy saves herself by using her powers to turn herself into a rat. Giles discovers the two dead children are actually a demon -- it's using the "Hansel and Gretel" ploy to get people to hunt witches. He shows the town people the demon in its true form, and they flee. Buffy destroys it with the stake she's tied to. But Amy is still a rat...
Buffy's 18th birthday draws near, and she is looking forward to going to an ice show with her father. But he has to cancel at the last minute. And worryingly, she seems to be losing her powers. Actually, Giles is secretly drugging her, on instruction from the Watchers Circle, so that she can take a Slayer test: defeat a vampire by skill and cunning alone. But the test goes wrong, and the vampire escapes, capturing Buffy's mother. Buffy does manage to defeat him, just, but her confidence in Giles is shattered. Then the Watchers decide Giles is too attached to Buffy, and sack him. So, all in all, another dreadful birthday.
Demons are intent on reopening the Hellmouth, but Giles is having difficulty getting the information he needs, because of his new sacked status. Xander is worried about his role in the Slayer's inner circle, as he is the only one without a special power -- as Cordelia misses no chance to remind him. He gets a new car, to try to be cool. But it attracts only a car nerd bimbo, then a psychopath with a big knife. While the others are desperately fighting demons, Xander has a little fling with Faith, then on his own has to stop zombies from blowing up the school. He succeeds, and, the next time Cordelia tries to bait him, discovers that cool comes from within.
Buffy's new watcher arrives. Wesley: "I've actually encountered two vampires, under controlled circumstances." Giles: "You don't get many of those around here." W: "Vampires?" G: "Controlled circumstances." Faith tries to persuade Buffy that slaying is fun : they slay, party, rob a weapons store, get arrested, escape, and slay. But then Faith accidentally kills a person -- the Mayor's assistant. Buffy is horrified, but Faith claims that she doesn't care. Also new in town is a gang of uniformed sword-weilding vampires searching for the demon Balthazar's amulet. The new watcher says Balthazar is dead, but actually he is just weakened, and is trying to rise against his old enemy. He captures the new watcher and Giles, who are rescued by Buffy and Angel. As Balthazar dies, he taunts them with the coming evil. The mayor casts a spell that gives him invulnerability for the next 100 days, prior to the rising...
As the mayor's assistant's body is found, Buffy tries to get Faith to realise the enormity of what she has done. Fragments of wood in the wound tell the Mayor that he was killed by a Slayer, and sets Mr Trick on them. Investigating the death, Faith and Buffy discover the Mayor is in cahoots with Mr Trick. As the net tightens, Faith tells Giles that Buffy killed the man -- but he doesn't believe her. Angel captures Faith, and tries to straighten her out -- he can empathise, having himself killed. But just as it seems he's breaking through, the new Watcher snatches Faith, to take her back to the Watcher Council for trial. She escapes. Buffy finds her at the docks, where they are attacked by a group of vampires led by Mr Trick. Buffy is trapped under a fallen crate, and is just about to be killed by Mr Trick, when Faith stakes him. Faith then goes to the Mayor, says she has killed Mr Trick, and asks for his job.
Anya wants back her powers, lost when her necklace was broken . She tricks Willow into helping her create a time fold, to retrieve it. But instead, the vampire Willow gets snatched just before she would have been staked in the finale fight. Meanwhile, Faith warns the Mayor that Willow is about to crack into his files. He says she will have to die, and sets a vampire gang on her. But they find the vampire Willow, who beats them and makes them her own. Buffy and Xander see V-Willow at the Bronze, and are distraught, thinking it is their Willow. They go to tell Giles, where they discover she is not dead after all. V-Willow and her gang invade the Bronze, where Anya tells her how to get home -- but she needs Willow helping with the spell. So she goes to the library, where Willow manages to hit her with a tranquiliser dart. To save the people at the Bronze, Willow dresses up in the vampire garb, to split the enemy before Buffy comes charging in. Cordelia finds V-Willow locked in the library cage, and frees her. She goes back to the Bronze, where in a big fight, the vampires are beaten, but no-one can bring themselves to stake V-Willow. Instead, they send her back to her own world, back to the finale fight, where, unknown to them, she is almost immediately staked...
A demon offers Buffy some mysterious books about the Ascension, for $5000. The mayor decides he wants them, and sends Faith off to recover them first. Faith goes to Angel, confessing worry about turning bad. But it's a ploy to get a special demon to take his soul again. Angelus and Faith then capture Buffy, and are about to torture her to death -- until Angel reveals it was all a trick to expose Faith .
While killing a demon, Buffy gets some of its blood on her -- which means she will take on one of its "aspects". No-one knows which aspect -- but it turns out to be hearing others' thoughts. To start with, this is fun, but gradually her friends become uncomfortable with her -- then it becomes uncontrollable, and all the thoughts overwhelm her. But as they do, she overhears a plot to kill all the Sunnydale High students. While Buffy lies almost catatonic, being gradually driven mad by the cacophony, the others have to discover who the killer is, before they can strike. Initially Buffy thinks it's Jonathan, who has taken a gun up into the school tower, but that was to try to kill himself, not the other students. Eventually a cure is discovered -- Buffy must eat some demon's heart -- which Angel gets for her. Recovered, she confronts the discovered killer -- the school cook about to poison everyone.
The Mayor has a strange box delivered, and gives Faith a big new knife. Buffy decides she must take the fight to the Mayor -- it's her only chance of leaving Sunnydale now that Faith has turned evil. So she and the gang steal the box -- but the Mayor captures Willow in the process. Buffy decides they must trade the box for Willow. During the trade they discover the box contains big evil spider-like creatures -- lots of them -- 50 billion of them. They get Willow back safely -- and she had managed to steal some important pages from the books of Ascension while held captive. Buffy realises she can never leave Sunnydale, and will have to go to the local University. Willow announces that she too will go to Sunnydale U, despite having offers from simply everywhere , because she has decided what she wants to do with her life: fight evil. And Sunnydale is certainly the best place to do that!
Despite the nearness of Ascension Day, everyone is getting ready for the Prom in their own way: the powerless demon Anya is trying to find a date, and asks Xander; Angel breaks up with Buffy, for her own good; a newly poverty-stricken Cordelia is working at a dress shop to buy her prom gown (and won't be able to go to college); and a rejected student is training devil hounds to attack people wearing tuxedos. Buffy is devastated by Angel's decision, but she recognises that he is right. She is determined to save the Prom for her friends, and manages to track down and kill the hounds. At the Prom she is recognised by her classmates as the reason for them graduating with a surprising low mortality rate, and presented with a "class protector" award.
Graduation Day is close at hand. Everyone knows this is the mayor's Ascension Day too, but no-one knows what to expect. Buffy gets her mother to leave town. Then Xander discovers Anya experienced a previous one, 800 yeas earlier, and it totally devastated the village where it occurred. Full demons are nothing like the half demons Buffy is used to slaying -- for one thing, "they're bigger". Anya tries to persuade Xander to leave town with her, but he stays with his friends. The Mayor gets Faith to kill a vulcanologist Professor. Buffy tries to find out why, and discovers details of an excavation which seem to have discovered the body of a demon below a lava flow -- the Mayor is only invulnerable until his Ascension, not after. Willow and Oz get closer. The Mayor confronts the gang in the library, taunting them. Giles snaps, and runs him through with a sword, but the mayor just pulls it out, wipes off the blood, and hands it back to Giles. [I really thought that would turn out to be significant later. Oh, well.] Faith shoots Angel with a poisoned arrow, so that his slow death will distract Buffy. The Council refuse to help save a vampire, so she turns her back on it. Eventually a cure is found, but it requires draining the blood of a Slayer. So Buffy sets off to kill Faith. They fight in Faith's new apartment, and Buffy does stab her, much to Faith's surprise, but she manages to fall into a passing truck, so that Buffy can't get her blood...
The Mayor discovers the scene of the fight, and orders his vampires to search for Faith. Buffy, having failed to get Faith's blood to cure Angel, offers him her own. Angel refuses, but she beats him up until he is too weak to resist. He drinks, but manages to stop just before killing her, and, cured, rushes her to hospital for a transfusion. In the next room lies Faith, not dead, but in a coma that the doctors tell a distraught Mayor is permanent. [I suspect they haven't taken her Slayer super-healing powers into consideration.] The Mayor discovers Buffy in the next room, and tries to kill her, but is stopped by Angel. While still unconscious, Buffy talks to Faith, who tells her the key lies in "human weakness". Buffy wakes, and, still weak, calls the team together to plan for the Ascension. They start assembling weapons and fuel, and packing up the library books. Buffy realises that the Mayor's "human weakness" is his feelings for Faith. The Mayor is the guest speaker at the Graduation ceremony, and, as the sky goes dark, transforms into a huge snake-like demon, and feeds on Principal Snyder. But the students have all been prepared and fore-armed, and start to attack the demon and his vampires. Eventually Buffy taunts the demon with the knife he gave as a present to Faith, to goad him into chasing her through the school. He does, and they end up in the library -- packed chock full of explosives. Buffy leaps out of the window, Giles sets off the explosive, and the demon, and most of the school, burns. Angel walks off into the mist, and the rest celebrate that they have survived ... High School.