La Femme secrète (1986)

Original title: La femme secrète

It was during one of his missions in Norway that Antoine learned of his wife's death. He leaves his experimental submarine and returns to Paris. Helene was found in the Seine and had taken barbiturates. Even though he had not been with Hélène for six years, he knew her well enough to believe that she was incapable of committing suicide. So who and why?