As commander of the powerful Special Branch, Thomas Pitt has the job of keeping Britain safe from spies and traitors. So there’s no obvious reason why he is suddenly ordered to investigate two minor incidents: the blood, hair, and shards of glass discovered outside the home of naval weapons expert Dudley Kynaston, and the simultaneous disappearance of Mrs. Kynaston’s beautiful lady’s maid.

But weeks later, when the mutilated body of an unidentified young woman is found near Kynaston’s home, Pitt realizes that this is no ordinary police investigation. Far from it. Is Kynaston—one of Britain’s most valuable scientists—leading a double life? Is Pitt saddled with a conspiracy so devilishly clever that it will ruin him?

A baffled Pitt has never needed his friends more desperately, including his indomitable wife, Charlotte; his canny old colleague Victor Narraway; and his personal drawing-room spy, Lady Vespasia Cumming-Gould. But even these allies may not be able to save Pitt—or Britain.