London, 1883. All is quiet at 125 Gower Street. Private detective Sidney Grice is studying up on the anatomical structure of human hair whilst his ward, March Middleton, sneaks upstairs for her eighth secret cigarette of the day. The household is, perhaps, too quiet. So, when a beautiful young woman turns up at the door, imploring London's foremost private detective to solve the mystery of her father's murder, Grice can barely disguise his glee. Mr. Nathan Garstang was found slaughtered in his bed, but there is no trace of a weapon or intruder. A classic locked-room case. But what piques Grice's interest is the crime's link to one of London's most notorious unsolved murders. Ten years ago, Nathan's uncle, aunt and servants were murdered in their sleep in the very same house. Now, it seems, the Garstang murderer is back.