Harold Hill is a con man who poses as a boys' band organizer and leader and sells band instruments and uniforms to the naive Iowa townsfolk, promising to train the members of the new band. But Harold is no musician and plans to skip town without giving any music lessons. Prim librarian and piano teacher Marian sees through him, but when Harold helps her younger brother overcome his lisp and social awkwardness, Marian begins to fall in love. Harold risks being caught to win her.