The former warship Trouble Dog and her crew follow a distress call from the human starship Lucy's Ghost, whose crew have sought refuge aboard an abandoned generation ship launched ten thousand years before by an alien race. However, the enormous vessel contains deadly secrets of its own.

The Marble Armada calls for recovered war criminal Ona Sudak to accompany its ships as it spreads itself across the Human Generality, enforcing the peace with overwhelming and implacable force. Then Sudak's vessel intercepts messages from the House of Reclamation and decides the Trouble Dog has a capacity for violence which cannot be allowed to endure.

As the Trouble Dog and her crew fight to save the crew of the Lucy's Ghost, the ship finds herself caught between chaotic alien monsters on one side, and on the other, destruction at the hands of the Marble Armada.