Robert and Cathy Wilson (Robert Donat and Deborah Kerr) are a timid married couple in 1940 London. He is a bookkeeper, she a bored housewife. However, their tedium-filled lives are drastically changed by the war. He enlists in the Royal Navy, while she (against his wishes) joins the Women's Royal Naval Service. During the three years the couple are apart, they are transformed, each becoming much more self-confident.