After hearing Cher's "Believe" for the umpteenth consecutive time, Buffy decides it's time for her nightly patrol. She tells Kathy that she's going out for a cup of coffee. Before Buffy can make it out of the room, Kathy mentions that some of the milk in their fridge is missing. Buffy confesses and takes off from Stevenson Hall. Outside, Buffy meets up with Willow, who listens to her friend talk about the trials of living with a new roommate. While Buffy and Willow part ways, a demon with orange wrinkled skin and glowing green eyes watches from behind the bushes. A sound nearby kicks Buffy into alert mode, but she soon realizes that it's only Kathy, who has decided to join Buffy for a drink. Suddenly, Buffy hears what is undoubtedly a growl. She pushes Kathy out of the way just as a demon attacks her. Buffy fights back, finally forcing the demon to retreat. As Buffy helps an unsuspecting Kathy out of the bushes, the demon rejoins his partner. They believe that they have finally found the one they've been after. The next day, Buffy visits Giles at his apartment. After she describes the demon to Giles, he wonders why Buffy is there instead of at school. Buffy admits that she's staying out of the dorm until Kathy goes to class. Meanwhile, Kathy futilely attempts to remove the stains on her sweater from the previous night. Giving up, she decides to take a look through Buffy's closet. Kathy finds a sweater to her liking, then notices Buffy's weapons bag on the floor of the closet. Later, Buffy cuts into the cafeteria line in an attempt to avoid Kathy, who is standing further down the line. The student whom Buffy cut off, Parker, decides to introduce himself. He gives Buffy a lesson on how to effectively utilize their meal cards. At the end of the line, Parker heads towards his friend's table, while Buffy joins Willow, Oz, and Xander at the other end of the dining room. During their conversation, Kathy takes it upon herself to join the group at their table, uninvited. Buffy quickly recognizes what Kathy's wearing, who believes that it's only fair since Buffy caused the stains on her own sweater. As Kathy tells the others about herself, Buffy watches in horror as a glob of ketchup falls from Kathy's hamburger onto the sweater. That night, Willow tries to talk on the telephone while her roommate throws a party at the same time. On the other end of the line, Buffy throws out more complaints about her roommate. Hearing Kathy just outside the door, Buffy hangs up. While Kathy sits on the bed and flosses her teeth, Buffy tries to fit her apple into the stuffed fridge, in which every item is labeled with Kathy's name, including each individual egg. When Buffy turns around, she realizes that Kathy has closed her window. Buffy opens it back up and hits the sack. After falling asleep, Buffy has a dream about a demon placing a scorpion on her stomach, pouring blood down her throat, and sucking a mysterious light out of her mouth. In the morning, Buffy tells Giles and the others about her dream. Kathy appears and tells them about a dream she had the previous night. While Giles and the gang are shocked to hear a description of the exact same dream, Buffy is more concerned with her growing irritation and hatred for Kathy. Later that night, the two green-eyed demons stand before a fire and begin to summon another named Tapparich. When Buffy returns to her dorm room, she finds Parker talking to Kathy inside. Apparently, they have been talking and getting to know each other for quite some time before Buffy walked in. After Parker leaves, Buffy and Kathy face off once again. This time, Buffy decides to help herself to as much of Kathy's carton of milk as she can handle. Elsewhere, Willow worries about Buffy steady change in personality. Oz tells her that he'll go find Buffy and see what's up. On his way to Buffy's patrol route, Oz passes by a group of students. One of them, a short girl, draws Oz's attention for a brief moment. As Oz looks back, the girl also does a double take with Oz, sensing something. Figuring it's nothing, Oz continues forward, failing to notice the army of rifle-carrying soldiers running towards the girl and her friends. During the patrol, Buffy tries to put her hatred for Kathy into words, but she only ends up destroying a park bench with a kick of pure hatred. Before going to bed, Buffy tries to get some reading homework done. However, Kathy's toenail clipping proves way more distracting than it should be. In retaliation, Buffy starts tapping her pencil. What follows is Cher's "Believe", Buffy's earmuffs, and the torturous crunching of Kathy's hard-boiled egg shell. Having had enough, Buffy goes to bed and has the same nightmare she had the previous night. Buffy wakes up the next morning to see Kathy squirming in her bed, apparently having the same dream. Later, Willow talks to Kathy in the dorm hallway about Buffy. Seeing Buffy approaching, Kathy takes off. Willow then listens in fearful concern as Buffy declares that Kathy is evil and must be killed. Buffy tries to explain that she took a sample of Kathy's toenail clippings and realized that they continued to grow by themselves. However, Willow has already concluded that her friend has gone off the deep end. Willow tells her to talk to Giles, then calls him up to warn him of Buffy's arrival. Buffy enters Giles' apartment and is greeted by a falling net from above. Giles, Xander, and Oz rush out to restrain Buffy with ropes, fearing that her murder plan must be stopped at all costs. Buffy leads Giles to the toenail clippings in her bag and tries to convince them that she's right. However, Giles believes that Buffy has been possessed by the demon she fought in the woods. While Xander and Oz take positions as watch guards over the restrained Slayer, Willow tries to warn Kathy about Buffy's intentions. Kathy's response of Buffy's come-uppance only scares Willow more, and she leaves shortly after getting a call from Oz. Back at the apartment, Buffy frees herself from the ropes and tricks Xander and Oz into coming close enough for her to knock them out. Buffy returns to the dorm room in hopes of finishing Kathy once and for all. When Kathy lands a hard backhand against her roommate's face, Buffy grabs her by the face and pulls with all her might. The human skin comes off, revealing the same kind of demon that Buffy encountered several nights ago. While they battle, Xander and Oz regain consciousness just as Willow arrives at the apartment. Back at the dorm, Kathy informs Buffy that she escaped from another dimension, and now her elders have followed her in hopes of bringing her back. The only way they can recognize one of their own is by sensing the absence of a soul, so Kathy has been sucking out Buffy's soul the past few nights. Giles learns of this Ritual of Mok'tagar through research and quickly checks the toenail clippings. Confirming their continuing growth, Giles goes out into the living room to tell Willow, Xander, and Oz what he has learned. Since Buffy has already escaped, Giles decides that he and Willow must perform a spell that will reverse the effects of the ritual. While Xander and Oz head towards the dorm, Buffy and Kathy tear up their room in the name of beating the crap out of each other. Just as Kathy attempts to finish her assimilation of Buffy's soul, Giles and Willow complete the spell. Buffy's soul leaves Kathy and returns to its original host. Suddenly, the demon Tapparich appears in their dorm room. Kathy tries to plead her case, but Tapparich has heard enough. He opens a portal that sucks Kathy and himself back into their own dimension. Now that Kathy is officially no longer a student at UC-Sunnydale, Willow decides to leave her party-crazed roommate and move in with Buffy. Things are finally looking up, although a forbidden bite from Buffy's sandwich drives the Slayer to focus her evil eye on Willow.