Laurence Payne is unhappily married to Patricia Danton. He's also carrying on an affair with her half-sister, Jane Griffiths. Jane coyly tells him she's enceinte. So he asks Miss Danton for a divorce. She refuses.
Well, this is a problem. He works out an elaborate murder scheme with Miss Griffiths, involving a tape recorder and exact timetables. It's a perfect scheme, except that Miss Danton is listening behind a door. As a result, when Miss Griffiths is murdered, all the rest of the evidence points to him.... except for one crucial piece.
It's a sick and twisted and very amusing murder mystery, with John Arnatt as one of those stolid, slow-talking and hardworking police inspectors. More like an expanded episode of THE ALFRED HITCHCOCK SHOW than anything else, it's a beautifully constructed, cheap little thriller.