At the end of the Tau Ceti trilogy, the library ship Capek has been taken over by colonists hoping to leave Trist, the colony planet of Epsilon Eridani. Knowing that Earth will eventually come for them, they decide to take Capek to another star not yet explored by Earth. They know that there is a planet with a breathable atmosphere but know little else about the planet. Gambling that they can survive there, they set out on a journey that will take years.
First, though, they must survive the trip.