The Empire is in decline. Only a few people realize that so far, but one of them is the Emperor, and another is Sander Cord. Cord and the Emperor grew up together, and he is the Emperor's closest (and maybe only) friend. They have formed a plan to try to preserve civilization when the Empire inevitably falls.
The Emperor has appointed Cord Viceroy of the Rim Sector, the only part of the Empire that is still dynamic enough and remote enough to have a chance of surviving the fall. After twelve years, their plan is about to succeed. The Emperor is about to grant the Rim Sector almost complete independence.
Unfortunately, a Rear Admiral commanding an Empire Fleet base and a powerful battle group has discovered the plan. The admiral knows he is being investigated for criminal activity. He plans to use his forces to seize the Sector, and then return it to the Emperor in exchange for amnesty. Anchoring the admiral's forces is the dreadnought Nemesis , a kilometer-sized ship carrying more armament than most planets.
Cord's own people have learned of the admiral's plan, but Cord has nothing with which to counter this overwhelming military force. Cord recruits Val Kedron, a trader captain with military experience, to organize and command a force to oppose Jonas.
Val puts his best friend and engineer to work with the best minds on the rim in an effort to find weapons that can be designed, built, and installed in existing civilian ships quickly. He also has to recruit a new astrogator, a deputy and flag captain to support him, and someone to command a ground-based resistance.
The astrogator Val finds is female, and he slowly falls in love with her. An old friend becomes his deputy and flag captain, and a marine major defected from the admiral takes command of ground-based resistance.
Val and his people must use ingenuity, imagination, and even a sentient ship to counter the admiral's massive firepower and salvage the Emperor's plan to preserve human civilization.