While on patrol, Buffy and Riley tag-team a vampire in the cemetery. Suddenly a blue, horned demon joins the vampire to form a tag-team of its own. While Riley serves the vampire a stake, Buffy makes fast work of the howling demon. Afterwards, Buffy and Riley are too turned on from fighting to report back to Giles. They choose instead to head over to Riley's for some "tension relief". Later that night, Riley wanders through the Initiative house, driven by an unknown obsession. When he arrives in the bathroom and turns off the dripping shower, he can finally go back to bed. The next afternoon, an ice cream truck pulls up to a curb in a quiet neighborhood. Behind the wheel is Xander, with Anya riding shotgun to keep her boyfriend company on his new job. Anya begins questioning his virility because Xander wasn't in the mood for sex the night before. The defensive Xander tells her that he'll have sex with her right then and there in the back of the van. When he starts unbuttoning his shirt, the only thing that stops Xander's kink is the fact that ten children and a parent waiting for ice cream are staring at him. Meanwhile, Buffy, Riley, Willow, Tara and Giles meet in a study room. They discuss the bizarre pairing of demon and vampire in the previous night's battle. Giles explains the rarity of an alliance between these opposing members of the undead. Before their discussion can get too theoretical, Buffy and Riley's hormones force them to leave for a pre-class quickie. Again that night, back in Riley's room, the horny couple copulates while other members of the Initiative stoke a fire in the living room downstairs. As Buffy and Riley's passion reaches a crescendo, a fireball erupts out of the fireplace and engulfs one of the unwitting soldiers. Forrest is barely able to smother the flames with a wall banner before his friend is seriously burned. The next night, Anya walks through downtown Sunnydale when Spike jumps out of an alley and grabs her. He tries to scare her into giving him money but Anya is far from frightened. When Spike asks why she isn't with Xander, he has obviously hit a sore spot with her. Over at the Initiative house, the young militia throws a raging party packed with college kids, including Buffy and her friends. Willow asks Xander where Anya is and he tells her that he just isn't in the mood for his girlfriend tonight. Meanwhile, Anya is at the Bronze having drinks with Spike. They both reminisce about the days when they had the power to make people do whatever they wanted. Tortured with thoughts of Drucilla and Xander respectively, they wish they were still evil enough to maim them both. Back at the party, one of the soldiers tries out some sleazy lines on a girl he's hitting on. When he puts his hand on the wall, an orgasmic sensation rushes through his body. After getting the girl to do it, he starts getting his friends to touch mysterious spot. Meanwhile downstairs, Xander flirts with an attractive girl named Julia, who digs his sense of humor. On the stairway, Willow and Tara discuss horseback riding. When Willow puts her hand on Tara's knee, Tara stands up disgusted and tells her to get away. The confused Willow tries to apologize but Tara runs into the bathroom. Just then, Anya and Spike show up at the party. Xander walks up and expresses his anger at Anya for trying to make him jealous. When Spike pokes fun at Anya's distressed boyfriend, Xander announces the arrival of Hostile 17 to the party. When none of the Initiative pay any heed to the scene, Spike realizes that they don't recognize him anymore and heads in to mix it up. Anya has had enough of Xander and breaks up with him on the spot. The infuriated couple goes their separate ways to enjoy their newfound single life. When Xander sees Julia in a spin the bottle game, he decides to join in. On his first try, the bottle lands on Julia who he gives a little peck on the cheek. Julia grabs Xander in a bizarre fit of passion and starts sucking on his face. When she snaps out of it and releases the liplock, she runs into a bathroom embarrassed. Meanwhile, Willow enters the bathroom that Tara ran into. The room is empty, but when she opens the shower curtain, she finds a little boy drowning himself in the tub. As Willow grabs a hold of him, he disappears. When she turns around, the pasty-faced boy is standing there staring at her. Downstairs the bottle from the spin the bottle game starts spinning like a top until it explodes. While these bizarre events unfold throughout the house, Buffy and Riley's love-making grows more and more intense. Xander, Willow and Tara all meet up and run to Riley's room to get Buffy. The door is entwined by living roots that grow and multiply sporadically. Suddenly, the house is rocked by an intense earthquake that causes the party-goers to flee. One girl runs right at Anya but passes through her like a ghost. Forrest and another soldier jump in the hidden Initiative elevator and head for the underground base to find out what is going on. Xander, Willow, Tara and Anya all regroup outside the front door of the house. The earthquake has stopped and the house is now deserted. When Xander tries to rush back in to find Buffy, he is ejected by an invisible force. The gang decides they need Giles to tell them what's going on. They rush to the coffee house where Giles told them he would be spending some adult time. When they arrive, they are shocked to find him in the center of the room, entertaining people with a song on his guitar. Back at Giles', Willow finds an old newspaper article detailing the use of the Initiative house as an orphanage back in the 50's. When they discover that the Mistress of the house, Mrs. Holt, is still living in Sunnydale, they decide to pay her a visit. The sweet old lady that begins telling them about her "children" turns out to have a deep rooted psychosis. Apparently she would punish the children for, what she considered, their impure hormonal thoughts. To cleanse the girls she would cut their hair off and to cleanse the boys she would hold them underwater in the bath. After Giles gives Mrs. Holt an earful for emotionally damaging children, the group storms out. In the hallway, Giles explains to them that whatever is going on at the house is a result of the energy released from the deep emotional trauma and spiritual damage to the children. The people they were seeing, like the girl who ran through Anya and the boy in the bathtub, were poltergeists rather than ghosts. They were released by the damage done to the children's souls so many years ago. The anomaly must have been caused by the intense sexual energy of Riley and Buffy lately. Giles explains that since Riley and Buffy are the catalyst, they will die if the poltergeist leaves before their sexual energy runs out. Tara takes Willow and Giles to her room to conjure a spell that will distract the poltergeists. This will buy Xander and Anya enough time to find Riley and Buffy. While the two Wickens and the Watcher concentrate, the poltergeists of the children suddenly appear around them. This allows Xander and Anya access to the house through the front door. As they make their way up the vine-covered staircase towards Riley's room, Willow, Tara and Giles lose the spell and the children disappear. Xander and Anya are instantly thrown from the staircase to the living room below. Xander's body is dragged through space to the bathroom. He is thrown into the bathtub and held underwater as the children appear around the tub looking in at him. Anya picks herself up and charges back into the vines, even as one tears through her hand. She fights her way to the bathroom and pulls Xander out of the water. Together they rush back into the living vines and battle their way through. The vines coil around them and slash at their faces like a snake pit. When they finally reach Riley's door and smash it open, Buffy and Riley separate to cover their naked bodies. This severing of the sexual coupling instantly evicts the poltergeist and causes everything to turn back to normal. The next day in the cafeteria, Riley and Buffy explain that some supernatural force was driving them to constantly make love and they had no idea what was going on outside the room. When Willow says how horrible that must have been, Riley and Buffy share a glance of disagreement.