John is only twelve - officially too young to join the Royal Navy - but he's determined to help conquer the approaching Spanish Armada. He also wants to seek vengeance against the enemy for his father's death at sea a year ago.
But conditions on board ship are far worse than he could ever have imagined - 'everything was strange: the foul smell, the creaking sound of the ship's movements, and the unfriendliness' - and the perils of naval battles present danger at every turn. But there's exhilaration and excitement aplenty too.
Vivid details of weapons, tactical manoeuvres, the conditions of prisoners and the wounded, and the fierce rivalry between enemy sides add to the excitement of this thrilling, short novel.