The trilogy continues. . . spoilers ahead for the first.
If you remember, Zaphod said they would go to the title restaurant for lunch. When this opens, they are trying to get the Heart of Gold there. Then they are attacked by a Vogon ship, begining the adventures, which involve a cup of tea, the Total Persepctive Vortex, the restaurant, a completely black ship with a half-built teleport device, Marvin being depressing, elevators with psychological problems, a ship full of useless people, and more.