Cannons at the Gate opens with a secret British mission to collect French gold as reparations just as Napoleon escapes Elba in 1815. When the cargo of gold is seized from the British ship returning to England, the vessel's purser, Ryan Boyle, is charged with piracy. Changing his name to Howard Moorhead with the aid of an uncle, he flees to New Orleans where he becomes a cotton merchant, marries a widow, and builds a plantation in St. Francisville...