July, 1806. Commanding a prison-hulk in the Medway guarding French captives, Martin Jerrold thinks his war can't get much better. He's far away from storm, battle and the other disagreeable elements of naval life, and he can keep his mistress, Isobel, close at hand; in fact, his most arduous duty is reining in the zealous Francophobia of his deputy. It seems too good to last, and so it proves.

When one of the prisoners, goes missing, Jerrold's comfortable world is turned upside-down. Summoned to London, he is ordered by the First Lord of the Admiralty to recapture the Frenchman at any cost. Jerrold does not know it, but his pursuit will take him clear across England: from the slums of London to the stinking marshes of Chatham; from the wilds of Dartmoor to the newly fashionable seaside resort of Brighton.

But who is this mysterious french man? At the Post Office, Jerrold's old friend, Mr Nevell, is curious; so too are politicians from the highest levels of the Whig government; as is the Tory opposition led by the cunning Spencer Percival. Even the seductive Princess Caroline takes an unexpected interest.

As Jerrold - with his usual mix of bad timing, bad luck and bad behaviour - closes on his quarry, he begins to uncover an extraordinary tangle of deceit and treachery stretching back over twenty years, which reaches to the most exalted levels of society on both sides of the Channel. And which some men will stop at nothing to protect.