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.
(thetvdb.com)