The Confidence Man.

Wade is a promoter of fake oil stock who sends two of his men, Dan Corvan and Larry Maddox, down to the small Florida town of Fairfield to make a sale to the miserly Godfrey Queritt (Charles Dow Clark). When Corvan discovers that Sunday school teacher Margaret Leland is friends with the old man, he romances her. He also helps out the local charities and endears himself to the local folk. Corvan is too good at his tricks -- all this hard-won trust is turning him into an honest man.