The First Slayer tells Buffy in a dream that "It is not enough".
Principal Wood tells Buffy to go home and concentrate on her "real" job, killing monsters and getting ready to battle the First. Buffy takes him to the house and introduces him to the rest of the crew, including Spike. The tension between Spike and Wood is tangible. Wood gives Buffy a bag that he got from his mother and should have been passed on to Buffy anyway.
Chloe commits suicide after the First talks to her all night. Buffy delivers a strong lecture, angering many of the others. She then calls an emergency and opens the slayer's bag. Inside is a set of shadow figures that trigger a portal. Against the advice of her friends, Buffy jumps in, sending back an enormous demon that beats everybody up and flees. After Spike recovers, he gets his leather coat out of a trunk, kills the demon, and drags it back to Buffy's house.
On the other side of the portal, Buffy is back in the desert where she once met the First Slayer. There, three men tell her she is the last slayer to guard the Hellmouth, and try to infuse her with the essence of the demon that give all the slayers their strength. Buffy refuses the power, telling the men that they were wrong to have created the slayer line in the first place. As a parting gift, one of them touches Buffy's head and gives her a vision (though the viewer does not immediately see what it is).
After struggling with the incantation, Willow manages to reopen the portal by sucking energy from Anya and Kennedy. Spike throws the dead demon in, and Buffy returns. Later, she tells Willow about the vision, and admits that the First Slayer was right that what they have is not enough. Willow asks Buffy what she saw, and the vision is shown to the viewer: Inside the Hellmouth, the First has an army made up of thousands of Turok-Han vampires.