It's the early 20th-century American Midwest. A con man going by the assumed name Harold Hill has used several different schemes to bilk the unsuspecting, and now travels from town to town pretending to be a professor of music - from the Gary (Indiana) Conservatory of Music, class of '05 - who solves all the respective towns' youth problems by forming boys' marching bands. He takes money from the townsfolk to buy instruments, music, instructional materials, and uniforms for their sons. However, in reality, he has no degree and knows nothing about music, and after all the materials arrive and are distributed, he absconds with all the money, never to be seen again. Many of the traveling salesmen in the territory have been negatively impacted by him, as the townsfolk then become suspicious of any stranger trying to sell them something. For Harold's scheme to work, he must gain the trust of the local music teacher, usually by wooing her, regardless of her appearance. And if the town doesn't believe it has a youth problem needing to be fixed, he will manufacture one for them. That is the case when he arrives in River City, Iowa, population 2,212, where he will have some unexpected help from Marcellus Washburn, a friend and former grifter colleague who now lives in River City and has gone straight, but he still wants to make sure Harold survives his stay in town. River City's music teacher is spinster and town librarian Marian Paroo. He's able to impress all the other River Citizens with his fast-talking sales pitches, but not suspicious Marian, whose hard-as-nails exterior is unlike all the other River Citizens. Her exterior is partly due to her somewhat removed standing in the town, as all the gossipy housewives believe she is a smut peddler - encouraging the teenagers to read authors such as Chaucer and Balzac - and mistakenly believe that she got her position as librarian through less-than-scrupulous means. What Harold does not know is that one way to Marian is through her young adolescent brother, Winthrop Paroo, a sullen boy who has withdrawn from life since their father's death two years before, when he started to lisp. Harold starts to fall for Marian, something that never happened with any of the other music teachers. Further complications may ensue if any of those traveling salesmen who have been following his route through the territory catch up with and expose him.