At the start of the American Civil War, German spy Gunter Rohlenheim is sent by Prince Otto von Bismarck to the United States to gather intelligence on the development of ironclad warships. Before Gunter can find his way to his intended target, his nemesis from ten years earlier sends an assassin to neutralize him.
Barely escaping death, Gunter is surprised whenhis investigation uncovers more advanced war technology being developed by the Confederate Secret Service in Mobile, Alabama. Angamar, an enigmatic old scientist, himself a refugee from Germany, connives to include Gunter into his development of a self-propelled torpedo when Gunter discovers the reincarnation of his own first engineering project, a submersible war ship.
The Confederate submarine experiment evolves into the CSS H. L. Hunley, and Gunter Rohlenheim, a German spy, using the alias Sam Miller, is consumed with the desire to become part of her crew. When the Hunley is called up of rduty as a blockade breaker in Charleston, South Carolina, Gunter is torn between loyalty to his homeland, the submersible, and an attractive war widow.
The fornsic reconstructions of the final crew of the H. L. Hunley sparked the idea of Convergence of Valor.