After his father is found dead, computer analyst Nathan Grey becomes the target of a group of murderous machines called the Bloc. After being nearly killed by one of them, Nathan is rescued by a member of the League of Allied Worlds, a secret organization consisting of humans and aliens. After being recruited into the League, Nathan learns that his father was also a member, and that his death is linked to the Bloc and his work with the League. Nathan's new position with the League takes him beyond the lunar base of Terra Vree to the distant world of Dreksess Major, and the city of Tabula Rasa. Throughout his adventure, Nathan survives repeated attacks by the Bloc while uncovering the secret behind his father's death. With little but his advanced technical background and limited combat training, Nathan and the other members of the League ultimately defeat the Bloc and save Tabula Rasa from total destruction.