At the center of reality abides a Family dedicated to guarding Time; but discord has torn them apart, putting the future--and the history--of Humanity at risk. Danny Nolan, a young doctor from our time, finds himself in the middle of the conflict when an unusual woman enters his emergency room. Tamara has just escaped an attempt on her life that has left her trapped in our time. Danny helps her, and is drawn into a new reality where time travelers can change history without being affected themselves by paradoxes, where sentient machines rule the Moon, and where colonies of humans modified by eugenics and nanotechnology fight each other for supremacy a thousand years in the future.