Fallen Idol (1948)

Baines, an English butler working at a French embassy, is more of a father to the ambassador's young son, Phillipe, than the ambassador. But the hated Mrs. Baines, the head housekeeper, is not a mother to him. Phillipe discovers Baines is having an affair with a young French woman working as a secretary in the embassy. But he's too young to realize what he knows. He believes Baines's story that the young woman is his niece, and he agrees to keep the matter a secret. Secrets and lies become the dominant themes of his young life -- especially when he thinks he's witnessed a murder.