Although she was well over forty when Happiness was filmed, Laurette Taylor was still specializing in girlish charm. Director King Vidor helped translate this charm to film when he helmed the motion picture version of Peg O' My Heart. It came out so well that Taylor and Vidor teamed up again for this film, another of the star's stage vehicles. Although the playwright, J. Hartley Manners, wrote the screenplay adaptation himself, this drama just didn't work well on screen. Jenny Wreay (Taylor) is a Brooklyn errand girl with an especially lively and cheerful demeanor. A wealthy young widow, Chrystal Pole (Hedda Hopper), finds Jenny's attitude appealing, and invites her and her mother (Edith Yorke) to live with her. Philip Candos (Cyril Chadwick), a jaded and world-weary friend of Chrystal's, brings Fermoy MacDonough (Pat O'Malley) into Jenny's life. MacDonough is an electrician and an inventor, and Jenny falls in love with him. Chrystal and Candos offer to use their wealth to help Jenny and MacDonough get a start, but the young couple prefer to do it on their own. Although it's a struggle, they manage to attain success and happiness.