An implacable alien intelligence called the Cluster has arrived in the galaxy and dissects almost every star ship it encounters. Grandson of an infamous space pirate, Commander John Mark Ellis is disgraced and booted out of the space service when he fails to save a merchant ship from the Cluster. Even so, Ellis believes he holds the key to communicating with the invader. His mother, Suki Firebrandt Ellis, is a historian who believes the galaxy's leaders are withholding information about the Cluster. Clyde McClintlock believes the Cluster is God incarnate and provides the path to salvation. G'Liat is an alien warrior who hopes to protect his people from the Cluster. All together, they set out to stop the Cluster's reign of destruction.