Ancient artificial intelligences called Angels are the shadowy guardians of civilization.  Over the long ages, humanity has become extinct and reseeded many times.  This is the 6th Epoch.  Little is known about the history of the first five.

Responding to a 20,000-year-old radio beacon, an expedition is sent an impossible distance across the galaxy in the hope of recovering knowledge of the origins of the human race.  An artifact is discovered in orbit around a dying star.  What the crew of the Erebusdiscovers could mean the end of everything.