Oscar Jaffe, a flamboyant Broadway impresario, transforms Mildred Plotka, a department store clerk, into the great actress Lily Garland, winning her both critical acclaim and a devoted following. For three years, Lily is both Jaffe's star performer and his mistress, although their relationship is tumultuous and marked by frequent arguments and reconciliations. When Lily decides to leave Jaffe and pursue a film career in Hollywood, Jaffe's career and financial prospects begin to decline.
Jaffe, accompanied by his manager Oliver Webb and press agent Owen O'Malley, boards a train bound for New York in an attempt to evade his creditors. On the train, Jaffe discovers that Lily and her fiancé George Smith, whom Jaffe dislikes, are also passengers. In an effort to win Lily back and secure her for his next production, Jaffe engages in a tumultuous and comical verbal exchange with Lily, trying to persuade her to sign a contract. The journey is further enlivened by the antics of two actors hoping to be cast in Jaffe's play, and a religious fanatic with delusions of wealth. When the train reaches New York, Jaffe has succeeded in tricking Lily into signing the contract.