On a foggy night, Michael Starkwedder enters the home of the Warwicks through a window in the study. He finds the dead body of Richard Warwick, and finds Richard's wife, Laura, holding a gun that supposedly killed him. Michael does not believe she killed him, and she soon tells him she is innocent. The two decide to place the blame on an enemy from the past, MacGregor, a man whose son was killed when he was run over by Richard's car while Richard was driving drunk. As the story progresses, it is revealed that Laura was having an affair due to Richard's cruel nature, and was vouching for the man she was cheating with when she claimed to have killed Richard.
Synopsis of scenes
The action of the play takes place in Richard Warwick's study in South Wales near the Bristol Channel. ACT I
Scene 1 – An evening in November. About 11:30pm
Scene 2 – The following morning, About 11am
ACT II
Late afternoon the same day
Reception
Philip Hope-Wallace of The Guardian reviewed the opening night in the issue of 13 August 1958 when he said, "The Unexpected Guest is standard Agatha Christie. It has nothing as ingenious or exciting as the court scene and double twist of Witness for the Prosecution but it kept last night's audience at the Duchess Theatre in a state of stunned uncertainty; guessing wrongly to the last. There are one or two irritating factors: an outsize red herring in the shape of what, naturally, one may not disclose; also one of those corpse's mothers who say, in so many words, "Inspector, I have not many years to live…" and embark on enormities of tedious repetition."
Mr Hope-Wallace said that the corpse was, "impeccably played with, no doubt, full assistance of the Method, by Philip Newman" and concluded, "I have known more tension and greater surprise from other of Mrs. Christie's classics but this is quite a decent specimen of her craft." Laurence Kitchin of The Observer reviewed the play in the issue of 17 August 1958 when he said. "The corpse cools unregarded in a wheel-chair while the widow and an intruder embark on a complicated exposition. Provided you can accept such unreality and the abysmal humour, there is an ingenious display of suspects, as if lids were being taken off wells of depravity and hastily put back." The Guardian reported that The Queen attended a performance of the play on the evening of 16 February 1959 with Lord and Lady Mountbatten. The cast were unaware that she was in the audience. It was also the night that Christopher Sandford fell ill part way through the performance and had to be replaced by his understudy after the interval.
It was adapted into an 1980 Italian television movie L'ospite inatteso. Many languages of Indian films have adapted the same story and made several versions. The 1973 movieDhund produced and directed by B. R. Chopra in Hindi language was one of the earliest adaptation and it went on to be remade in Marathi in 2012 as Don Ghadicha Daav. The Kannada language adaptation of the play was titled Tarka and released in 1988. The Kannada movie was remade in Tamil in 1990 as Puriyaadha Pudhir but the Malayalam remake version titled Chodhyam also made in 1990 never had a theatrical release. The Kannada movie was remade in 1997 in Hindi as Chupp. A radio dramatisation adapted and directed by Gordon House was broadcast by the BBC on 30 May 1981.