June 1914. On a rain-swept night, an open car pulls up at a hotel in the modest spa town of Bad Ilidže, deep in the Dinaric Alps of Bosnia-Herzegovina. The driver, wet through, is Thomas Jaeger, an Englishman who has been working for British Military Intelligence for the past 12 years. He is burnt out, his life in ruins. An Austrian couple are guests at the same hotel. The following day they will travel a short way along the valley to the next town by train. The town is Sarajevo. Within four hours, both husband and wife will have been murdered. The wife is Sophie Chotek, Duchess von Hohenberg. Her husband is Franz Ferdinand, Archduke and heir to the Hapsburg throne. The countdown to war has begun.
In London, Military Intelligence has discovered that a rogue agent is on the loose somewhere on the continent. With war drawing ever closer, any such person could threaten the integrity of the security services and the very existence of the realm. One man has the skills to track him down. Jaeger. But others are also joining in the hunt, foreign agents who want Jaeger dead. Foremost among them is a Serbian secret society. The Black Hand.