It is the Civil War and Colonel Michael Baker rules Fort Harmer. The old Fort, on the Delaware River a few miles south of Philadelphia, has been converted into a prison to hold captured Confederate soldiers. Baker is the commandant of Fort Harmer; he and his assistant, Major Jonathan Kelly, have turned the prison into their personal kingdom. Their tentacles reach far beyond Fort Harmer through a vast network of bribes, intimidation, murder, and corruption. But even Colonel Baker eventually goes too far and draws the attention of the War Department. In the summer of 1864, Secretary of War Edwin Stanton sends U.S. Army Major Thomas Lamond to Fort Harmer with orders to destroy Baker's corrupt empire. Lamond, a combat veteran battling demons of his own, arrives at Fort Harmer and finds himself overmatched by Baker and Kelly. Still, with the help of a Confederate sergeant being held prisoner, Lamond sets about bringing down Baker, Kelly, and their prison fortress in the swamps of the Delaware River.