In 1912, con man Professor Harold Hill arrives in fictional River City, Iowa, to swindle the citizens. A few traveling salesmen in the area have heard about Hill, who is known for a ploy in which he gets townspeople to pay to create boys' marching bands, with Hill faking his musical expertise and skipping town once he has their money. Hill discovers that River City is the home of his former associate Marcellus Washburn; with Marcellus's help, Hill incites a
moral panic among River City's parents that their boys are being seduced into sin by the town's new pool table. He suggests that a marching band will keep young boys out of trouble. Anticipating that Marian Paroo, the town's librarian and piano teacher, is suspicious of his motives, Hill sets out to seduce her. Also suspicious is Mayor Shinn, owner of the
billiard parlor, who orders the school board to obtain Hill's credentials. When they attempt to do so, Hill distracts them by teaching them to sing as a
barbershop quartet. Thereafter, Hill tricks them into breaking into
four-part harmony whenever they ask for his credentials. Hill's wooing of Marian, who mistrusts him, has little effect, though he succeeds in winning the admiration of her mother and befriends her unhappy younger brother, Winthrop. When Marian discovers that Hill's claim to being a graduate of Gary Conservatory is a lie, she attempts to expose him, but is interrupted by the arrival of the
Wells Fargo wagon, delivering the band instruments that the townspeople had ordered. When Winthrop, after years of moody withdrawal, joins in the townspeople's singing and speaks effusively about his new
cornet, which had arrived in the wagon, Marian changes her mind about Hill. Hill tells the boys to learn to play via the Think System, in which they simply have to think of a tune over and over and will know how to play it without ever practicing on their instruments. Meeting Marian at the traditional footbridge—the first time she has ever been there with a man—Hill learns that she knows of his deception but did not tell because she is in love with him. He is about to leave town when Charlie Cowell, a disgruntled anvil salesman who was run out of
Brighton, Illinois, because Hill had conned the townspeople there, comes to River City and exposes Hill. Sought by an angry mob and pressed to leave town by Marcellus and Marian, Hill realizes he is in love with Marian and does not want to leave. Hill is captured by the mob and brought before a town meeting to be tarred and feathered. Marian defends Hill; the townspeople, reminded of how he has brought so many of them together, relent. Mayor Shinn reminds the townspeople how much money Hill has taken with no apparent result. When he demands to know "Where's the band?" Hill is saved by the town's boys, who play
Beethoven's
Minuet in G. Although their technique is awful, the parents are enthralled. As the boys march out of the town hall, they are suddenly transformed in the townspeople's imagination into a band, playing and marching with perfection, led by Hill, much to Charlie's shock and clumsiness via hurting his toe by dropping his anvil case. ==Cast==