The twenty-fourth century: humankind has become a spacefaring civilization, colonizing the solar system and beyond. While no alien forms of life have yet been encountered in this expansion into space, colonists suddenly encounter machines of alien origin—huge robots able to reproduce themselves. Called replicators by the colonists, they seem to have but a single goal: to destroy all organic life they come in contact with.

Since the colonial governments have no means to fight this menace directly, they instead promise huge rewards to whoever destroys a replicator. As a result, the frontier attracts a new kind of adventurer, the Hunters, who work to find and destroy the replicators. Mike Edwards, a skilled young maintenance technician and robotics expert at a faraway outpost, will not only become one of them—but be the very first one to unlock the secret behind the replicators' origin and mission.