Arriving late at night in the seaside town of Seagate, Jim Medway (Derek Farr) heads for his estranged wife’s isolated coastal cottage. As he arrives, he sees local businessman Charlie Durham (William Hartnell) coming out of the house, in which he then finds his wife dead. With the awareness that his wife had been having an affair with Durham, Medway embarks on attempts to blackmail the rich entrepreneur or get him arrested for murdering his wife.