Rot ist die Liebe (1957)

Poet Hermann Lons is turning 40. On his birthday, his childhood love, Rosemarie, unexpectedly to visit her cousin (who just happens to be Hermann's wife). Rosemarie and Hermann walk through the Luneburger Heide every day and it isn't long before their old love flares up again. Hermann is rather annoyed about that and asks the woman to leave. His decision, however, brings him no joy. Luckily, he's able to deal with his grief by writing poetry, which brings him some success. But now his life is one big, melancholy drama, punctuated by too much alcohol. When Hermann eventually learns that Rosemarie has gotten engaged to Hermann's hunting buddy, Prince Niko, he realizes he wants to ask his wife for a divorce and chase after his former lover. Luckily(?), Rosemarie puts the brakes on the whole thing saying it's too late for them.