In the nursery of a hospital that is funded by Variety Clubs International, Barbara Stanwyck explains to Joan Caulfield how the Variety Club charities were founded.  Eighteen years earlier, in 1928, in Pittsburgh, Pennsylvania, a baby girl was left in the Sheridan movie theater with a note from her parents calling on the generosity of those in the film business to take care of her.  An usher places the infant in the care of members of the Variety Club, a group of eleven local showmen who meet once a week.  The men decide to sponsor the child and put her up for adoption as Catherine Variety Sheridan.

Eighteen years later, only four people know who Catherine is: The Browns, who are her adoptive parents, J.R. O'Connell, who runs Hollywood's Paramount studio, and Bill Farris, head of Paramount's New York office.  Catherine, who is now a talented singer performing under the name Amber La Vonne, contacts Farris, and he asks O'Connell to set up a screen test for her.  A scarcity of rooms at the Hollywood Girls Club causes a gutsy, but talentless unknown blonde actress to impersonate Amber in order to steal her room.

When Catherine arrives, the actress befriends her, but insists on keeping her stage name.  After "Amber" pulls off a stunt in the Brown Derby restaurant and shamelessly calls attention to herself, Paramount talent scout Bob Kirby arrives to pick up Catherine, but mistakenly leaves with "Amber."  "Amber" is then given Catherine's screen test.

Later, believing "Amber" is Catherine, O'Connell invites her to a party at his home.  At O'Connell's, "Amber" pretends to be a temperamental starlet and demands that Kirby let Catherine sing at the party.  Despite the antics of Spike Jones and his orchestra, who have been ordered by Kirby to disrupt her performance, Catherine proves that she can sing.  Before she can ingratiate herself with O'Connell, however, Catherine inadvertently pushes him into his pool, sending him into a rage.

Afterward, on the set of a Cecil B. DeMille film, Catherine again soaks O'Connell.  To punish "Amber" for foisting herself and Catherine on him, O'Connell orders William Bendix to purposefully humiliate her during her screen test by recreating over and over the grapefruit scene with James Cagney and Mae Clarke grapefruit scene in the film The Public Enemy.  "Amber" becomes so angry that she pushes the grapefruit into Bendix's face and throws a tantrum.  At Farris's suggestion, O'Connell asks "Amber" to sing at the Variety Club's show, and Kirby arranges it so that Catherine's voice will be dubbed in.  Because Catherine has, in the meantime, soaked O'Connell for a third time, she arrives dressed as a cigarette girl and hides under a table to sing.  "Amber" allows Catherine to receive her own applause, however, and O'Connell is about to have Catherine thrown out, when Farris tells him who she is.  The Variety Club's show then ends with performances by an all-star cast, including Bob Hope and Bing Crosby impersonating Siamese twins.