The Longitude Chronometer, a device that will change the world, is stolen from HMS Petrel by pirates working for the legendary but supposedly long dead Edward Teach - better known as Blackbeard. On board the Petrel is Tom Lowe, an English spy working undercover as ship's surgeon. Lowe's mission is to prevent the Chronometer from falling into the hands of pirates... and if the opportunity should arise, to assassinate Blackbeard.

When Kate is captured on a trading voyage, Blackbeard and Lowe must work together in order to rescue her before she reveals the island's whereabouts to William Jagger. In the process, Lowe discovers that Blackbeard has an ulterior, deeply personal motive for keeping him on Santa Compana.