Two months ago, several monks rushed to perform a ritual while a powerful force of some sort threatened their lives. In the present, Buffy stakes a vampire outside an abandoned building, and then gets caught by the night watchman who thinks she's a teen looking for a rave. As she turns to leave he tells her not to forget her glow-ball, an orb which Buffy doesn't recognize but takes to investigate.
Buffy makes breakfast for her mom, who is still suffering from headaches that the doctors can't explain. Dawn takes credit for the breakfast, telling Joyce that Buffy only helped. Joyce and Dawn bond (Joyce calling Dawn her pumpkin belly), which leaves Buffy feeling like an outsider. Giles' big opening is less than successful at first, but eventually, the magic shop gets to be so popular that he can't handle it all on his own. Buffy presents the orb to Giles, but Giles can't explain it right away, though he recognizes it as paranormal in origin because "it's so shiny".
While picking up a prescription for her mother at the hospital, Buffy encounters the night watchman again as he's being strapped down to a gurney. He's less than stable, but he manages to warn Buffy that she will be attacked through her family.
A monk works on a blueprint in an empty building just as The Beast smashes through a large steel door, revealing itself to be a supernatural blond female. The Beast tries to torture information about the Key out of the monk, but he won't tell her anything. She starts to speak crazily until she puts her fingers to the head of a security guard and seems to suck the life force from him.
Buffy assumes that the danger she was warned about is what is causing her mother's headaches. Anya recommends to Buffy that she perform a spell to reveal any spells that may be affecting her family. Buffy doesn't want Riley to feel unwanted, so she offers to let him help her with the spell. He realizes what she's doing, then they talk and agree to take care of each other.
Buffy performs the ritual in her bedroom then walks around her house to look for anything unusual. Nothing appears weird about her mother, but Buffy sees Dawn's image flashing in and out of pictures around the house. When she enters Dawn's room, Buffy sees Dawn's possessions, bed, desk, and decorations also fading in and out. Buffy confronts Dawn about it, and she concludes that Dawn isn't her sister. Buffy threatens Dawn, telling her to stay away from their mother, but Buffy's supposed little sister appears truly confused and doesn't understand Buffy's sudden change in attitude.
Giles calls to tell Buffy about the orb, a Dagon Sphere, and its purpose of protection from an unnamed evil. Buffy returns to the abandoned building in hopes of finding more information. Buffy encounters Spike lurking outside her home and demands to know what he was doing there. He begins to answer and she demands that he give his response in five words or less. He pauses and, counting four fingers, says "Out, for, a, walk", and then sticks up his thumb and says "bitch". She is unsatisfied with his explanation, and he responds: "Contrary to one self-involved world view, your house is directly between... parts and other... parts of this town." She agrees to let him off with a warning, and he becomes frustrated, saying that she needs some satisfaction in her life besides what she gets from "Captain Cardboard", and that he (Spike) has never liked her anyway, and that she "has stupid hair." Spike then leaves. Looking down, Buffy notes a bunch of Spike's discarded cigarette butts; he must have been loitering there for several hours. Shaking her head, she proceeds to return to the warehouse as Dawn watches the whole exchange from the window.
Buffy comes up against the Beast and finds herself unable to effectively counter the Beast's incredible strength. After taking quite a beating, Buffy is able to escape with the monk. The Beast throws a tantrum, causing the room to collapse on her, which delays her pursuit. Back at The Magic Box, Giles offers Anya a job when he realizes that the job is too much for just one, and that she enjoys handling the money.
In his last moments of life, the monk warns Buffy that she must protect the key. He tells her that the key is a collection of energy put into a human form, Dawn's form. They sent her to the Slayer to be protected from those looking for it. Before he dies, he tells her that her memories of Dawn were constructed, and that Dawn is now an innocent human who not only needs the protection of the Slayer, but also the love of a sister. When Buffy returns home, she apologizes to Dawn, and the two girls are able to relate on at least one subject - their concern for their mother.