At 12 years old, John Barr is cruelly separated from his father and pressganged into the Navy. Now a powder monkey onboard the mighty HMS Fearless, John has his first taste of bloody sea battle and soon learns that the ship hides many secrets.

His new knowledge thrusts John into a shadowy world of naval espionage, right to the centre of a covert operation. Accompanied only by fellow shipmate, Kit, he must go ashore into hostile territory and outwit a nest of French spies. But when disaster strikes, the friends find themselves abandoned behind enemy lines...