La beauté du diable / Beauty and the Devil (1950)

Professor Henri Faust, retiring after 50 years as an alchemist in a circa-1700 university, despairs at still knowing nothing of the true secrets of nature…whereupon his old acquaintance Mephistopheles, servant of Lucifer, appears and grants him youth and a new life. But with youth, Faust's interest is diverted from science to women. And Mephistopheles, who has taken on the guise of the elderly Faust that was, sets many snares for his young friend's slippery soul…