Napoleon has won the Battle of Waterloo and England is under French occupation. A half-drowned girl washes up on a Cornish beach, escaping French soldiers after the murder of her black sea captain father. An aristocratic soldier-spy, haunted by his part in the defeat at Waterloo, plans to spring the Duke of Wellington from captivity. Together, they become enmeshed in a web of treachery and espionage stretching from London to the Scilly Isles.