Escaping the planet Molx, Commander Carpenter discovers that the colony ship Marco P and its computer have been commandeered by an external power. He cancels plans to continue on to their intended destination until they regain control of their ship. Backup Navigator Maelstrom, who had destroyed her computer interface to free the colonists from Molx, believes that she can navigate without computer assistance.

With help from the race that aided Earth's expansion into the galaxy, the Marco P can finally proceed. However, the power that commandeered their computer still lurks on their path. What's more, Carpenter and his crew learn that their destination already possesses a space-traveling, militaristic civilization. Is the mission doomed to fail, or does humanity possess a special mystique that will bring about success?