Morse and Lewis investigate the murder of Harry Josephs, a warden at St. Oswald's church who is found dead immediately after a church service. The initial focus is on a tramp who attended the service but the autopsy reveals that Josephs died of an overdose of morphine. When others who attended the same service are killed - including the vicar Lionel Pawlin, the church organist Paul Morris, his 12 year old son and Harry Josephs' wife Brenda - Morse suspect that everyone who attended that particular service is in danger. However, the solution to the case revolves around deceit and mistaken identity.