Astronaut Christian Brannock achieved immortality when he allowed his consciousness to be uploaded onto a computer. Billions of years later, when AI's called nodes control the galaxy and the survival of Earth is threatened by the expansion of the sun, Brannock is summoned to investigate the condition of humanity's home planet. He will soon meet another mind-that of a woman named Laurinda Ashcroft, who chose to merge with an Earth-based computer. Together, they must explore a simulation of Earth and all of its alternative pasts and futures, run by a rogue robot whose ambivalence toward human existence may hide far more dangerous secrets ...