Former soldier Andrea Herrera isn't happy with where her life's taken her. Specifically, Hell Creek, Montana, 65 million years before the present. As far as careers go, making sure the dinosaurs don't eat her paleontologist clients comes in a pretty dismal second choice to serving her country. But when their time machine malfunctions, Andrea and her team are trapped in a timeline that shouldn't exist with something a hell of a lot more dangerous than terrible lizards: other humans.

Kidnapped by the stone-age descendants of a lost time colony, Andrea finds herself stripped of her technological advantages and forced into a war against the implacable armies of the Slaver Empire. Even worse, the Slavers have captured the time machine and the mission's one surviving paleontologist, using his futuristic weapons for their own ends.

Andrea's only hope lies with the ferociously intelligent and violently insane tribal war-leader, Trals Scarback. Armed with his mystic sword, his trained velociraptor, and his herd of war-triceratops, this former slave has the resources and motivation to take on the empire. But can Andrea persuade him to see her as a partner rather than a tool for his ambitions? Only if she beats the barbarian at his own game and becomes the Tyrannosaur Queen.