Superintendent Thomas Pitt of Bow Street is up against the most sensitive and politically demanding case of his career. There is a traitor at work in the Colonial Office, passing confidential information to the German Embassy, and the expansion of the Empire is at stake. The field of suspects is limited to a handful of highly distinguished public servants. Simultaneously, Pitt is quietly looking into the death of a childhood mentor, who has apparently taken an overdose of laudanum. What possible connection can there be to the hidden traitor.