Die große Liebe (1931)

Ten years after the end of World War I, Austrian soldier Franz leaves Russia and returns to his village, where he is reunited with Frieda, a woman who believes he is her long-lost son. She seeks him out and greets him with such loving joy, that Franz doesn't have the heart to tell her the truth. He stays with her and when he gets to know his new girlfriend Annie, he begs her to hide his true identity from Annie. Annie, for her part, has seen through this charade already, but chooses to say nothing and to continue to care for Franz.