Buffy tries to figure out if and how Spike has been killing again. Spike finally remembers what he's been doing. Dawn doesn't tell anyone about her ghostly mother's full warning. Giles gets involved in the international killings by the robed guys. More...

Under instructions from the shapeshifting evil thing, Andrew goes to the butcher to get more blood to put on the seal in the high school basement, since knifing Jonathan didn't seem to do the trick. There, he runs into Willow, who is getting blood for Spike, and she drags him back to the Summers home where Xander and Anya grill him for info. Principal Woodside finds Jonathan's body, removes it, and buries it elsewhere. Buffy tries to reach Giles, and when she can't, she calls the Watcher's Council. The Watcher's Council is pleased to learn that Buffy doesn't know what's going on, and give her no info on Giles. Spike goes crazy again and goes after Andrew. Buffy chains Spike in the basement, but the house is attacked by robed men and Spike is kidnapped. Buffy recognizes the robed men and realizes they're fighting the First Evil. The Watcher's Council realizes that the First Evil has declared war, so they declare war on it, but then they are blown up. The First Evil tells Spike that he should have taken care of Andrew. Spike is stabbed and then hung bleeding over the seal until an ancient vampire arises. More...

After one of the potentials is convinced to commit suicide by the First, Buffy issues a challenge to everyone around her to step up their game. Robin Wood gives Buffy some of his mother's old things, and, through some Slayer relics, Buffy finds herself transported through a portal to the world of the creators of the original Slayer. Spike steps up his game and gets back to his violent roots, taking down the enormous demon that came through the portal through which Buffy disappeared. Buffy defies the creators when they offer her more power by violating her the way they violated the first Slayer. Willow steps up her game and harnesses strong magicks to bring Buffy back from the shadow world. Kennedy gets a taste of what Willow's power is really all about. Robin Wood tries to learn more about Spike and the possibility that Spike killed his mother.

Andrew decides to film what's going on at Slayer Central for posterity, but he drives Buffy nuts while he's doing it. Buffy and Robin find that the students at the high school are going insane, and it's all because of the mysterious seal in the basement. Through some research, Willow realizes that since Andrew was the first to start opening the seal, he might be able to close it. Buffy takes Andrew to the seal, and while Robin and Spike battle crazed high school students upstairs, Buffy threatens to spill Andrew's blood on the seal to close it for good. Andrew finally repents his evil ways and the murder of his best friend, and when his tears fall on the seal, the seal loses its power. Buffy admits she just threatened Andrew to get him to cry. Robin tries to stake Spike in the back while fighting by his side, but is distracted at the last minute. Xander and Anya fall into bed together one last time, and although they admit they still love each other, they realize they finally have closure. Kennedy starts to get close to Willow again after being scared off for a little while.

Giles returns with a mystical device that will determine if Spike is still under The First's control. The device shows that Spike's trigger is still active. Spike remembers that the trigger song is one that his mother used to sing to him, and remembers siring his own mother and then being horrified by her telling him that she never loved him. Giles thinks Buffy is being foolhardy keeping a dangerous Spike alive, and colludes with Robin to distract Buffy while Robin goes after Spike. While fighting off a vengeful Robin, Spike realizes that his mother did love him, and the cruel things she said to him as a vampire were just a demon talking. He also realizes that Robin not only wants revenge on his mother's killer, but feels like his mother never prioritized him over her "mission" as a Slayer. Buffy rejects Giles after figuring out that he was stalling her while Robin went after Spike, and she warns Robin not to try anything like that again. Willow gets a call from Fred in Los Angeles and leaves town for a couple days to take care of something.

Buffy makes peace with Robin who fires her and tells her to concentrate on preventing the apocalypse. Willow brings a mostly-reformed Faith back with her from Los Angeles. A mysterious priest named Caleb comes to town. Caleb, who is a disciple of The First, was the one who blew up the Council in England, and he controls the Bringers that hunt down the potentials. When Caleb sends a message to Buffy with a nearly dead potential, Buffy takes the challenge and leads her ragtag army into battle. Buffy and her gang are surprised when Caleb turns out to be unworldly strong and cruel. Caleb kills some of the potentials, injures many others, and blinds Xander in one eye. Buffy retreats.

As Buffy's gang reels from their encounter with Caleb, the residents of Sunnydale begin to evacuate, and those that stick around, like the Sunnydale police, start to feel the effects of the evil in town. Caleb finds Buffy at the closed Sunnydale high school, and gives her another good beating. Giles sends Spike and Andrew north to a monastary that Caleb once inhabited. A monk there shows them an inscription that infuriated Caleb: "It is not for thee, is for her alone to wield." Faith takes the girls out to the Bronze to blow off some steam, but the dancing and drinking ends in a brawl as cops arrive and try to beat the crap out of Faith. Buffy decides that they should go after Caleb again because he must be protecting something at the vineyard, but everyone around her decides they don't like her leadership anymore and turn to Faith for guidance.

Faith tries desperately to lead the girls while Buffy retreats morosely to an abandoned house. Faith comes up with the idea to kindap a Bringer and interrogate it, but what they learn only confirms the fact that Buffy was right, and they have to go back to the vineyard. Spike returns with news from the monastary, and runs to find Buffy when he realizes she's been ousted from her own house. Spike's words of wisdom and cuddling through the night give Buffy much needed strength. The First visits Faith in the form of The Mayor and tells her to beware of Buffy. Faith easily seduces Robin Wood while Kennedy finally gets a night alone with Willow. Anya and Xander find themselves sharing ice cream in the kitchen which turns to passion on the kitchen floor. Buffy goes back to Caleb's lair and dodges him artfully, finally sneaking into a trap door in the floor of the vineyard. Faith and the girls find Caleb's arsenal of weapons and battle a lot of Bringers, only to accidentally set off a huge ticking bomb. Buffy finds a mysterious weapon in a stone.

After the explosion, the injured girls try to find a way out of the cavernous armory, but find themselves surrounded by Ubervamps. Luckily, Buffy saves them with her cool new scythe that she just pulled from solid rock. Anya and Andrew have a bonding moment over what it means to be human when they go to loot the hospital for medical supplies for the girls. Buffy and Spike finally admit their true feelings to each other. The First tells Caleb that his power is waning, so The First and Caleb merge again so that Caleb is reinfused with evil power. Buffy asks Xander to take Dawn and get out of Sunnydale, but Dawn stops Xander and turns the car around to go home. Willow and Giles research the scythe and send Buffy to an unconsecrated tomb for more info. There, Buffy meets the last of the Guardians, who forged the weapon. The Guardians have been around since the Shadow Men created the first Slayer and then became Watchers. Unfortunately, Caleb kills the last Guardian and battles it out with Buffy. Just when it looks like Buffy is done for, Angel steps in and saves her, although Buffy finishes off Caleb on her own. Buffy kisses Angel in her happiness to see him. Spike watches from the shadows and The First whispers in his ear.

Buffy kisses Angel, but admits to him her feelings for Spike, which a slinking-away Spike misses. Angel gives Buffy a powerful amulet to be worn by one "ensouled," and Buffy immediately goes home and gives it to Spike. She and Spike talk about her encounter with Angel, and she tells him she sent Angel away. Buffy and Spike spend the night together. Buffy realizes they have to go into the Hellmouth and destroy what is there, rather than waiting for The First's army to come after them. Willow casts an incredibly powerful spell turning all potential Slayers into actual Slayers, and the gang of girls are suddenly serious opponents for the army of Ubervamps under the seal in the basement of the high school. While guarding for escaping Ubervamps and Bringers, Anya dies saving Andrew life. Spike's amulet activates itself and he goes up in flames as the amulet begins to destroy the Hellmouth... and all of Sunnydale. Buffy and her friends escape to the outskirts of town just in time to witness the whole city fall into a huge crater. They realize they've changed the world, now that there are Slayers everywhere.