This detective story features an old couple: Prudence Colonel and Bélisaire Beresford, who live a tranquil life - until Aunt Babette visits them and tells them that she has witnessed a murder in a passing train. The aunt has reported what she has seen to the authority, but as no dead body has been found, everybody thinks she must be dreaming. However, as Prudence is bored, she begins to investigate and finds that perhaps her aunt was right. The clues lead her to the castle of the Charpentier family and to enter, she works there as a cook. Then Prudence finds the dead woman's body in a sarcophagus.
This is a very good adaptation of Agatha Christie's 4.50 from Paddington. In the book, Miss Marple is the detective; but here it's the Beresford couple. Agatha Christie also created the Beresford couple: Tommy and Tuppence; and here their names are changed. The tone of the movie is comedy and it was fun to watch. Films based on Agatha Christie's books made in England mostly are faithful (to the books), so it's nice to see this creative adaptation made in France.