Lacey Flint, Sharon Bolton's enigmatic protagonist, has been living in a houseboat on the River Thames, and she's becoming a part of London's weird and wonderful riverboat community. Against her friends' better judgment, she's taken up swimming in the Thames, and she feels closer than ever to Detective Mark Joesbury, despite his involvement in a complicated undercover case. For the first time in her life, as she recovers from the trauma of the last few months, Lacey begins to feel almost happy.

Then, at dawn one hot summer morning while swimming down the river, Lacey finds the body of a shrouded young woman in the water. She assumes it was chance―after all, she's recently joined the marine policing unit, and she knows how many dead bodies are pulled out of the river every year, most the result of tragic accidents. But further investigation leads her policing team to suspect the woman's body was deliberately left for Lacey to find. Lacey's no longer a homicide detective, but as she begins to notice someone keeping a strangely close eye on her, she's inexorably drawn into the investigation.

Award-winning author Sharon Bolton has once again crafted a tightly plotted, utterly unpredictable thriller around one of the most compelling characters in crime fiction today, intensely private London police officer Lacey Flint, whose penchant for keeping secrets is only matched by her determination to uncover those of others.