In a gloomy flat off Islington High Street, Chief Inspector Brett Nightingale and Sergeant Beddoes find an old woman dead. The Princess Olga Karukhin, who fled from Russia at the time of the Revolution, has lived in terror of being discovered ever since. Olga's grandson, Ivan, appears to have run from the scene, but is later seen returning to the flat as though oblivious to the terrible crime. Taking place between 22nd and 24th December, Nightingale's enquiry takes him across London, culminating in the wrapping of the mystery on Christmas Eve.