Both Kathy and Buffy are both having strange dreams about a demon who pours blood down her throat, sucking her essence from her mouth, and putting a scorpion on her stomach. The major possessive Kathy becomes about things in the dorm, the more Buffy increasingly starts to believe that Kathy is evil. She decides since she fights evil, Kathy must be killed.
Buffy is ambushed by Giles, Oz, & Xander when she goes to Giles's place to show them Kathy's growing toenails she has in a baggie. They tie her up and try to make her see reason. She escapes and goes back to her dorm where she fights with Kathy. In the battle, Buffy rips off Kathy's face to find the same type of demon from her dreams. Kathy tells Buffy she escaped her dimension to go to college and fears her family will come to take her back. She wanted to borrow Buffy's soul so that her family, which takes the soulless, would take Buffy instead of her.
Meanwhile, Giles realized Buffy was right about the toenails being evidence of a demon. He casts a spell to return the parts of Buffy's soul Kathy had taken thus far. Kathy's father appears, opens a portal, and takes her back to their dimension.
In the end, Willow has become Buffy's roommate.
This episode originally aired on October 12, 1999.