Post office messenger boy Dave Martin has promised his father that within a month he will abandon his obsession with rock and roll if the tape recording that his group, "The Smart Alecs," has made is unsuccessful. After several frantic attempts to get an audition, Dave loses the tape recording when he is hit on the head while delivering a package to a film studio. Mark Watson, an American film producer, discovers the tape and is enchanted with it. He searches for the boys, who finally make a successful audition by playing over the intercom of the taxicab in which Watson is a passenger.