Five months after the end of the Civil War, Acting Navy Lieutenant Everett Townsend is awaiting discharge in Key West. The end of the war has left him uncertain about his future and full of regret about the end of his relationship with Emma, the Cuban American daughter of a Havana boarding house owner. His Spanish grandmother—a slave owner who runs a prosperous sugar plantation in the Cuban countryside—is dreaming that Everett will return and take over the family business, a prospect that sickens him.

Returning from a routine supply mission from Fort Jefferson in the Dry Tortugas, he and his men are caught in a hurricane and witness a shipwreck in the Marquesas Keys. When they investigate, they discover a locked cargo hold with the dead bodies of Black freedmen. When Townsend reports this unsettling incident to his distracted Naval commander in Key West, he's encouraged to drop the matter. But he can't shake his suspicions that the poor souls from the cargo hold were destined for re-enslavement in the sugar fields of Spanish Cuba.

The murder of an American sailor in a Cuban port provides Townsend with a reason to return to Cuba and continue his investigation. A rescue of a Navy veteran leads to more clues and helps convince Townsend to become a government informant operating in the interior of Cuba.