After an unusual energy surge reveals their presence, Tyke and the other survivors find themselves attacked by an aggressive and ruthless group of military colonists who escaped from Earth just before the plague. Determined to get the secret of Tyke's Orion Strain vaccine so they can return to take over the world, they are prepared to do whatever it takes to force the information out of him. The survivors soon find themselves locked in a bitter struggle over the future of humanity, and over who will inherit the Earth after all.