An old woman is found murdered at home. In her mouth is a playing card, the Queen of Clubs. DCI Marcus Priestley finds a connection to a dying woman, but she and her only living relative have watertight alibis. He searches for other crimes where the obvious suspects could not have been the perpetrators. Believing there may be a broad conspiracy behind the various cases, he sets out to unravel the web of connections. DI Penny Baker arrives to run the original murder investigation. She is attracted to Marcus and tries to impress him with high-risk behaviour. Following unsuccessful abduction attempts on them, they are thrown together for protection. They pursue a connection to a drug dealer, leading to a violent and tragic outcome.