At Firenze, the reclusive artist Adrian Delafield's Florentine enclave in St John's Wood, the whispers of an impending tragedy are growing louder. The tension between the fanatical zealot of a housekeeper Miss Trimming and Delafield's sister Virgilia is just shy of fever pitch, when a cold morning at the house finds Trimming and Adrian sprawled at either end of the staircase – upstairs, an injury; downstairs, death. The windows and doors were all locked from the inside, and yet Inspector Julian Rivers, trained to see the malice behind deadly accident, suspects that a murderer had a hand in the fell deed. But if this is true, Rivers is faced with both the inexplicable puzzle of motive, and the task of untangling an impossible crime.