Overview
The Scapegoat is a 1959 British mystery film based on the 1957 novel of the same name by Daphne du Maurier, and starring Alec Guinness, Nicole Maurey and Bette Davis.
Plot
John Barratt (Alec Guinness), a lonely, discontented teacher of French at a British university, is on holiday in France. There, by chance, he meets his double, French nobleman Jacques De Gué (Guinness again). They become acquainted. Barratt becomes drunk and accepts De Gué's invitation to share his hotel room. When he wakes up the next morning, Barratt finds himself alone in the room, with his clothes missing. De Gué's chauffeur Gaston shows up to take his master home, and Barratt is unable to convince him that he is not the nobleman. Gaston calls Dr. Aloin, who diagnoses (over the phone) the Englishman as suffering from schizophrenia.
A bewildered Barratt allows himself to be taken to De Gué's chateau, where he meets "his" family: daughter Marie-Noel, wife Françoise, sister Blanche and formidable mother the Countess. None of them believe his story - it appears that De Gué is a malicious liar - so Barratt resigns himself to playing along. As time goes on, he feels needed, something missing in his sterile prior life.
The next day, brother-in-law Aristide discusses business with him. Later, in the nearby town, Barratt is nearly run down by De Gué's mistress, Béla, on her horse. He spends the usual Wednesday afternoon tryst getting acquainted with her. The next time they meet, before he can confess the truth, she informs him that she has already guessed it.
From Wikipedia (CC BY-SA 4.0).