THELH is the loneliest man in the universe. After eight thousand years of life experience, no place, and no person, retains their intrigue for very long. THELH is a wandering soul, journeying from world to world in search of something to break the monotony of his life. Then THELH arrives on the planet Miraval. Then he meets intergalactic fugitive Za'Xophopah, and for the first time in his long life, things begin to change.

Alexander Gillespie is telling a story to a lecture hall of students. Through their derision and disbelief, he tells the story of a robot indistinguishable from a man, and a beautiful woman with a lot of secrets. He tells the story of alternate realities and parallel worlds, where the consequences of a person's life can ripple through time to reshape the course of the past and the future. Professor Gillespie tells the story of the creation of God.

Subject 0 is dead. Its consciousness has been uploaded to a database within the Nexus, and with the help of a sentient computer algorithm, Subject 0 relives the circumstances leading up to its demise. It remembers Lysander Sarth and the Ventrarius Device, THELH and Alex, a desert world burning under two twilit suns, and a world trapped forever at the end of all things. A lifetime ago, Subject 0 died. And now it must return to the world it left behind.