Starring Burt Lancaster and Jean Simmons, Elmer Gantry is about a fast-talking traveling salesman named Elmer Gantry (Lancaster) who always seems able to talk his way out of any problematic situation, as well having the knack to talk anyone into just about anything. This particular talent comes in handy for a traveling salesman in the 1920s. Elmer seems to feel as if he is doing fairly well in his traveling circuit until he meets Sister Sharon Falconer (Simmons), a traveling evangelist who preaches hell, fire and brimstone and seems to have an ability all her own to draw the crowds.
Elmer finds himself taken with Sister Sharon and soon manipulates his way into her good graces and into a position of being invaluable to the evangelist in her organization. Realizing the tremendous opportunity that is put before him, Elmer quickly parlays Sister Sharon's popularity into a profitable business, thanks to the immense number of her followers. Not surprisingly, Sister Sharon finds herself falling for Elmer as he also falls for her. However, Elmer's former reputation isn't one of the most well-received ones, and it doesn't take long before those he swindled in the past are soon looking for their chance to pay him back for his deeds.
Through his manipulation of Sister Sharon's popularity and his own cunning personality, Elmer is able to have the Crystal Cathedral built as Sister Sharon's home base for her ministries. Just as it seems that everything is going in a great direction, a woman comes forth and accuses Elmer of illicit behavior with her. The irony is that the accusation is a false one motivated by revenge. Although Sister Sharon refuses to believe the accusations and remains true in devotion to Elmer, and the charges are proven to be false, both meet with a tragic ending as their beloved cathedral burns, and they refuse to leave.