Diana Stewart (
Sylvia Syms) and Mark Paxton (
John Thaw), are in love, however, Diana's husband Geoffrey (
Noel Johnson) is unlikely to grant her a divorce. When it is discovered that Geoffrey has a mistress, the two begin planning his murder. One night, as he is preparing to go on a month-long holiday, Mark shoots Diana's husband; Diana arrives shortly afterward to help him get rid of Geoffrey's body. They put it in the back of a car. Things start to go wrong when the body disappears from the car and Diana later receives a mysterious telephone call from her "deceased" husband. Diana is told by Geoffrey to meet him at a local motel or he will go to the police and have her arrested for attempted murder. Much to Mark's dismay, she is told to come to the motel alone. Mark soon receives a phone call from a local shopkeeper, Kitty Tracey (
Patsy Smart), who informs him that Diana has been arrested at the motel after the police discovered Geoffrey's body. This is not the case, and the couple believe they are "home and dry" until they are preyed upon by a mysterious blackmailer. == Main characters ==