After years of pushing the boundaries of interstellar spaceflight, Commander Maya Davis is ecstatic when she is promoted to captain. But her enthusiasm wanes when she discovers that her new assignment is a one-way mission.

After taking command of the space-time vessel Yesterday, Maya must travel back in time to discover how and why a piece of 23rd century technology appeared 200,000 years earlier. It's an exciting opportunity--except for the one-way aspect. The best minds of her time say it's impossible to return to the present.

Trapped in the distant past, Maya must choose between a peace that could condemn humanity to perpetual slavery, or a fight for freedom that involves deception, rebellion, and mass murder. Whatever she decides, her actions may very well erase an entire civilization from history.