The Burning Crucible [Le Brasier ardent]

A woman, named simply "Elle" and her husband, a wealthy industrialist, are not on the best of terms. While she enjoys the way he caters to her every whim, she wonders whether he really loves her. He, on the other hand, torments himself by imagining rivals. One morning she awakens from a nightmare in which she has been pursued by a man in various guises, who turns out to be the famous Detective Z, whose memoirs she has been reading. When she and her husband quarrel over leaving Paris permanently for a country estate, he goes to the "Trouve Tout" Agency and hires, of all people, Detective Z, to win back her affection.