When British spymaster Sir John Oldmixton offers Benjamin January a hundred dollars to find the murderer of an Englishman whose body has been found floating in the New Basin Canal, Benjamin turns him down immediately. As a free man of colour in New Orleans in the sweltering July of 1839, he knows this is not something he should get mixed up in.

But when clues to the dead man's identity link the death to another murder, in another July in January's past, he is reluctantly drawn into the investigation. Nine years ago in Paris he failed to catch a killer - with tragic consequences. Now in New Orleans he must unravel the earlier murder, the one that took place during the great revolt against the Bourbon kings, to solve the second killing. At stake is not merely a hundred dollars, but hidden treasure, the fate of an innocent woman - and the lives of January's wife, son and unborn child.