An underground mansion in Hammersmith lies empty. A warren of corridors and rooms, lit by artificial bulbs that mimic different times of day. A swimming pool of dark water ripples in silence. All sounds and light are muted. But in one room, a computer glows. On the screensaver floats the words: Who Am I and What Have I Done? Stella Darnell, the detective's daughter, is convinced that this is a crime scene. But what was the crime? And who was the perpetrator? As she and Jack, a train driver, follow the faintest of clues back into the past, they come to a week in 1977 when the nation was obsessed with catching the Yorkshire Ripper. A week when nobody would notice a lonely dogwalker, strangled in Richmond Park.