What is at the end of the universe?

The Restaurant at the End of the Universe continues the story from where The Hitchhiker's Guide to the Galaxy ended. Arthur Dent, Ford Prefect, Trillian, and Zaphod Beeblebrox have just left the planet Magrathea when they are attacked by a Vogon ship. Luckily, an ancestor of Zaphod's, Zaphod Beeblebrox the Fourth saves them, but Zaphod and Marvin oddly vanish, only to turn up at the offices of the Guide on Ursa Minor Beta. They are looking for Zarniwoop, who has gone on an intergalactic cruise in his office via his virtual universe. Arthur, Trillian and Ford are unaware of any of this, knowing only that the computer has been shut down, and only having received a message from a stalling Nutrimatic that says "Wait."