John Grey is visited at his London office by Thomas Cade, a shipbuilder, who tells Grey he has evidence that Samuel Pepys is taking substantial bribes in his position at the Naval Office. Grey sends him on his way, telling him he has little chance against such a powerful man as Pepys — and then the following morning Cade's stabbed body is found in the grounds of Lincoln's Inn

Later that day Grey meets up with his benefactor Lord Arlington who tells him the king himself wants Grey to investigate corruption in the Naval Office — and it occurs to Grey that by dismissing Cade to his death, he has now lost his best witness and informant. He begins his investigation by questioning the dead man's wife — who it transpires was having an affair with Pepys... as were a great many other ladies. And as the investigation becomes increasingly hampered while the Court closes ranks and threats made against his life, Grey begins to suspect that Arlington's agenda is less to do with reform of the navy and more to do with gaining an advantage over his rivals at Court ...