Elmer Gantry is a fast talking, hard drinking traveling salesman who always has a risqué story and a hip flask to entertain cronies and customers alike. He is immediately taken with Sister Sharon Falconer, a lay preacher whose hellfire and damnation revivalism has attracted quite a following. Gantry uses his own quick wit and knowledge of the bible to become an indispensable part of Sister Sharon's roadshow but soon finds that his past catches up with him in the form of Lulu Bains, now a prostitute. While Gantry seeks and eventually gets forgiveness from Sharon, tragedy strikes when she finally manages to get out of her revivalist tent and opens a permanent church.
A fast-talking traveling salesman with a charming, loquacious manner convinces a sincere evangelist that he can be an effective preacher for her cause.