After a classmate of Phoebe is murdered by a demon to stop her thesis proving demons exists from being published, Phoebe and her sisters set out to vanquish the demon called Libris so a past victim can move on to the next plane of existence. However, the ghost is unable to move on until she helps Prue solve the murder of another young woman. Piper's preparation at the club for a performance of the Goo Goo Dolls is cut short when Dan arrives with some surprising news about Leo.

Prue, Piper, and Phoebe's relaxing night at the club is cut short when they're forced to go up against the Four Horsemen of the Apocalypse, who are causing various bouts of road rage in San Francisco. When Prue and Horseman of War are sucked into a vortex that transports them to the Netherworld of Good and Evil, Piper and Phoebe are facing a dilemma of saving Prue or save the world. While attempting to help the sisters out, Leo tries to get his bosses to aid the Charmed Ones and comes across organized evil.