A dentist cleans up the West with the help of a reformed lady bandit.

In the 19th century, Jesse W. Heywood graduates from a Pennsylvania dental college and heads west to set up a frontier practice. En route, the stagecoach on which he is riding is robbed by two masked bandits, one of whom is pretty Penelope Cushings, alias Bad Penny Cushings. She is caught by a sheriff's posse and agrees, in exchange for a full pardon, to help the government learn who is smuggling guns to renegade Sioux Indians. Then, in order to board a wagon train that does not accommodate single women, Penelope dupes Jesse into marrying her. The marriage is not consummated, however, because of a Sioux attack on the wagon train, much to Penelope's relief and Jesse's gawky chagrin. During the attack, Jesse believes he is responsible for killing more than a dozen braves, when in fact it was Penelope who scored the kills. Soon Jesse is known as the fastest gunman in the West, and the formerly timid dentist begins wearing elaborate outfits to reflect his fearsome reputation. Shattered when he learns the truth, he confesses his incompetence to the townspeople, who immediately shun him. Jesse finally proves his mettle when Penelope is captured by the Indians: disguising himself as a squaw, he rescues Penelope, helps her uncover the gun smugglers, and even shoots fairly well.