Queen Victoria privately asks Thomas Pitt to investigate the death of Sir John Halberd, a trusted confidant found in the Serpentine with evidence of a fatal blow. Halberd had been examining illicit weapons sales and possible treason, making his death a threat to the crown as well as a murder.
Pitt, Charlotte and their allies follow a trail through government, industry and imperial ambition. The final case in the series tests whether service to queen and country requires silence or the exposure of men whose patriotism conceals personal profit.