After leaving New South Wales, Jack Aubrey discovers that a transported woman, Clarissa Oakes, has been smuggled aboard Surprise by a young officer. A hurried marriage protects both of them from immediate punishment but cannot prevent suspicion and sexual tension from spreading through the ship.
As the voyage continues among Pacific islands, Stephen Maturin learns Clarissa’s history and recognises that she possesses information about a leak inside British intelligence. Private trauma becomes part of the wider espionage plot following the circumnavigation.