Gary Cooper is an ambulance driver who is in the middle of combat in World War II. Life is tenuous for everyone. He meets a nurse, played by Helen Hayes, who has just lost her fiancé to the war. They hook up and he leaves. The result of their encounter is her pregnancy. Because Cooper is friends with a carouser with whom he inhabits bars and brothels, his friend, feeling that Cooper could be harmed by this woman's situation, intercepts letters she has sent to him. So she feels he has no feelings for her. He sends letters to her, but she has been transferred to another unit hospital. So communications have broken down and this leads to great pain. The ending is quite emotional (perhaps a bit too emotional) with some real overacting from two really good actors. Hemingway, apparently, hated the movie version of his book. It's worth a look but there are better movies featuring his work.