Twentieth Century is the comedic story of Oscar Jaffe, a successful and egomaniacal Broadway director, who has transformed a chorus girl, Lily Garland, into a leading lady. As Lily rises to stardom and heads to Hollywood, Oscar begins a career downslide. Bankrupt and on his way out, Oscar boards a train, the Twentieth Century Limited, where he coincidentally runs into Lily again. Oscar pulls out all the stops to persuade the now temperamental star to return for another show.