Le Loup des Malveneur (1943)

A legend about the Malveneur family tells of how their ancestor sold his soul to the devil and was cursed: man by day, wolf by night. The last of the Malveneurs is a scientist who carries out strange experiments on... nobody knows exactly what the does in the underground. The wife has a heart condition, her sister-in-law is a authoritarian lady. And nights in the old castle are not exactly peaceful.