Frustrated by his inability to write original songs while he is awake, or remember the tunes that he writes while he is sleeping, Arkansas hillbilly Lester Robin travels to New York City to receive instruction from Harry Miller, a songwriter with whom he has been taking a correspondence course. At Harry's apartment, Lester meets Billie Shaw, an aspiring dancer, and instantly falls in love with her. Although Lester has lost his money, Harry, who with his partner Teddy, has gone broke trying to sell a song to musical producer Paul Plummer, invites him to stay. A tired Lester soon falls asleep on Harry's couch and begins composing a catchy tune out loud. As the song pours out of him, Harry and Teddy copy down every note and word, then rush to Billie's apartment, where Plummer and radio "crooner" Kenny Baker are visiting. After claiming the song as his own, Harry performs for Plummer, who recognizes the composition as a "sure-fire" hit. Now the musical talk-of-the-town, Harry and Teddy, who have already plundered Lester's dreams for another song, throw a lavish party in their apartment. There, Harry proposes unsuccessfully to Billie, who in turn rejects the proposal of Kenny because her older sister Gertie, who is in love with Lester, is still single. At the climax of the party, Lester falls asleep in Gertie's arms and reveals his songwriting ability to her. At the same time, Plummer signs Harry to write the score for a new musical revue but stipulates that the songs must be finished by the next morning. Desperate to succeed, Harry and Teddy prepare to put Lester to sleep, but when Teddy tells him that Billie and Kenny are engaged, the love-struck Lester develops instant insomnia. In spite of Harry and Teddy's night-long attempts at putting Lester to sleep, the depressed hillbilly remains awake until Billie telephones and tells him that she is not engaged. Overjoyed, Lester falls asleep and starts composing Harry's new score. As planned, Harry's show opens at Radio City Music Hall, but Gertie, who is determined to win Lester for herself, exposes Harry's deception to Plummer during the performance. Forced to give half of the show's royalties to Lester, who has fallen in love with Gertie, Harry announces that Lester is his new "protege," and the now engaged Kenny and Billie perform the grand finale.