When Harold Hill, a traveling con man, arrives in River City, he convinces the locals to start a band by purchasing the uniforms and intstruments from him. His intention is to flee as soon as he receives the money. Librarian Marion Paroo suspects Harold is a fraud but holds her toungue since her moody brother, Winthrop, is excited about the band. As Harold begins to develop feelings for Marian, he faces a difficult decision about skipping town.