London, March 1918. British newspapers carry the dire news that the German Spring Offensive has begun, with thousands of British lives lost. Against this sombre backdrop, further mayhem strikes in the capital when a fire provides the diversion needed for an audacious bank robbery which leaves a police officer dead in its wake.

For Detective Inspector Harvey Marmion, the investigation has a personal connection. However, the task of bringing the culprits to justice will be an uphill battle without Detective Sergeant Keedy, who is anxious to be released from hospital, at his side. And nothing in this case is quite what it seems .