 DI Jack Frost investigates a series of commercial robberies. He s assisted by DC Carl Tanner, a black officer recruited by Supt. Mullett to encourage racial balance on the local force. When Frost makes an arrests on the local housing estate, Mullett s only concern is the culprit s racial background as he s concerned that the area not become a racial powder keg. When Frost s informant on the estate is killed, the case becomes a murder investigation, but all of the suspects are black and racial tensions are on the rise. In the course of his investigation, Frost determines that his informant had a number of secrets.