Hercule Poirot appears on David Frost's talk show with actor Bryan Martin. The two are joined by Martin's costar Jane Wilkinson, who is later revealed to be a Wilkinson impersonator named Carlotta Adams. Adams' impression of Wilkinson is so perfect it fools Martin himself. Martin, Poirot, and Poirot's assistant Captain Arthur Hastings attend a dinner party, where the real Jane Wilkinson corners Poirot and asks for his help getting her a divorce from her husband, Lord Edgeware. Poirot agrees, only to discover that Lord Edgeware has already granted the divorce.
The next day, Lord Edgware is found dead. His staff insist that Wilkinson must have killed him, since she had threatened to once before. Inspector Japp is ready to arrest Wilkinson for the crime, but she has an alibi: she was at a dinner party with 12 other people. After Carlotta Adams is also murdered, Poirot investigates, much to Japp's annoyance. In the end, it is revealed that Jane Wilkinson did in fact murder her husband, hiring Adams to attend the dinner party in her stead in order to give herself an alibi. She then killed Adams to ensure her silence.
Sue Lloyd as Woman speaking in Background at a meeting (uncredited)
Production
Thirteen At Dinner was the first of three television films featuring Sir Peter Ustinov as Hercule Poirot. All three were given contemporary settings, rather than being set in the era in which they were originally written. Ustinov had appeared as Poirot in two previous theatrical films after taking over the role from Albert Finney.[6]
