Summer 1679 and a Balthasar St Michel is fighting a duel – and winning. A second-generation immigrant, the son of a displaced French aristocrat, a survivor in a foreign land, Balty is obliged by circumstance to become an expert predator. Balty is also the Navy's Muster Master at Deal – but this time he is in serious trouble, accused of stealing the cargo of an English vessel.

Balty is hoping his brother-in-law’s influence as the highest official in the Navy Office will save him – but he is shocked to discover his brother-in-law has been imprisoned in the Tower of London, charged with treason and in peril of his life.

Balty rises eccentrically and magnificently to the challenge of saving him, tracking through the labyrinthine intrigues of Louis XIV's Paris and coming to realise that behind his lethal adversaries lurks an English Duke – and that perhaps his brother-in-law, one Samuel Pepys, is not quite to be trusted either …