The president of the United States has broken the nation's number-one commandment, and by doing so has put himself in the crosshairs of America's number-one counter-terrorism operative, Scot Harvath.

Prologue, two years previously: Guantanamo Bay, Cuba. In the dead-of-night, five of the most dangerous detainees in the war on terror are pulled from their isolation cells, held at gunpoint, and told to strip off their orange jumpsuits. The prisoners are issued civilian clothes and driven to the base airfield, where they are loaded aboard a black Boeing 727 that whisks them away to freedom.

Flash forward to the present day: Scot Harvath awakes to find that his girlfriend, Tracy Hastings, has been killed, and that the assassin has left behind a very strange calling card. The doorframe above Harvath's entryway has been painted with blood, but not just any blood. Analysis indicates that the killer used lamb's blood tainted with a unique radioactive isotope. The isotope is part of a top-secret program the United States developed to covertly track the movements of the nation's worst enemies.

Angered with the lack of cooperation he is receiving, and against the direct orders of the president, Harvath mounts his own operation to hunt down Tracy's killers and to exact revenge. It's a quest that will thrust everything he holds dear, including his life, into absolute peril.