In the Middle Ages, a young man approaches a horned demon, who smiles at him and then breaks his neck. Later, a group of monks, outraged by the deed, chant in Latin, open a book and the demon is sucked into it -- its pages now filled.

Back in the library, Buffy opens a crate and finds the long forgotten book. Along with Xander and Willow, the school's two computer experts are helping scan books: Fritz, a menacing looking bruiser, and Dave, a geekier kid. Also present is Miss Calendar, the computer science teacher, who rides Giles about his fear of technology. As Willow scans the ancient book, the characters disappear from its pages. When she looks away, words appear on the screen: "Where am I?"

A week later, Willow tells Buffy about Malcolm, a boy she's having an online romance with. Buffy, worried about her naive friend enlists Dave's help to try to find out more about Malcolm. Dave tells Buffy to leave Willow alone. Meanwhile, Miss Calendar stumbles upon the ancient book and asks Giles about its blank pages. When Giles notices the horned demon on the cover, he suspects trouble. Dave gets Buffy to look for Willow in the girls' locker room but when she gets there, Fritz has rigged up some wires in the shower to try to electrocute her. A puddle reaches the exposed wires and Buffy is sent flying into the locker room -- the soles of her shoes smoldering. A shaken Dave tells the computer he can't kill Buffy. Angry at his disrespect, it types up a suicide note for him.

Back in the library, Giles explains to Buffy and Xander that in the Dark Ages, the souls of demons were sometimes trapped in certain volumes, where they remained harmless until the pages were read aloud. When Willow scanned them, the demon, Moloch, was unleashed into the computer, and how had access to any computer in the world. Moloch preys on impressionable minds, which makes both Fritz and Dave vulnerable to his power. Buffy tries to delete Willow's files, hoping to "delete" Moloch along with them, but Moloch appears on the screen warning Buffy to stay away from Willow.

Looking for Willow in the computer lab, she finds Dave's body hanging, with the suicide note pinned to it. Fritz goes to Willow's house, chloroforms her and brings her to a mysterious warehouse where Dave had been spotted earlier.

A desparate Giles asks Miss Calendar for help and discovers she has extensive knowledge of the mystical realm. She helps him repeat the spell the monks had chanted while she links up a configuration of different computers around the world.

Meanwhile, Buffy and Xander try to save Willow at the warehouse. By the time they arrive, Moloch has left the computer and appears as a robotic incarnation of the horned demon that was back in the Dark Ages. He breaks Fritz' neck and is about to break Willow's when the spell takes hold, immobilizing him. Injured, but fighting, he lunges at Buffy, but she ducks and he punches a high-voltage junction box and is electrocuted to death.