By late 1759 it is clear that France is losing the Seven Years War. In a desperate gamble, the French Atlantic and Mediterranean fleets combine to dominate the Channel and cover a landing in the south of England, but they are annihilated by Admiral Hawke at Quiberon Bay. Meanwhile, a diversionary landing is planned in the north of Britain, and it sails from Dunkirk before news of the disaster at Quiberon Bay can reach its commander. The ill-fated expedition sets out to circumnavigate Britain in an attempt to salvage something from the failed strategy.
George Holbrooke, newly promoted to post-captain and commanding the frigate Argonaut, joins a squadron sent to intercept the French expedition. The quest takes him to Sweden, the Faroes, the Western Isles of Scotland and then to Ireland and the Isle of Man. The final act is played out at a secluded anchorage in the Bristol Channel.