In Hollywood at Columbia Studios, music department director and vocal coach Phil Young meets with producer Joe Brady, who is anxious to find a female vocalist to team with their top star, singer Frankie Laine. Meanwhile, messenger Suzy Mulligan meets newcomer Cathy Blake and shows her around the studio, revealing that many of the girls who take the messenger job hope it will lead to their being discovered. Unknown to anyone at the studio, Cathy is the granddaughter of wealthy Pasadena socialite Martha Blake, who abhors show business and believes Cathy has started work at the local library. That evening at home, Cathy learns with dismay that her unpleasant cousin, Elliot Livermore, is helping Martha organize a benefit for her favorite charity. Elliot fully supports Martha's old-fashioned idea of having a retired Navy admiral speak at the benefit with Cathy singing stuffy songs from Martha's youth. Martha's butler and close friend, Tobias, knows the truth about Cathy's job and heartily encourages her. The next day at the studio, Cathy gets her first assignment, delivering sheet music to Phil. Dismayed by the singing auditions he has been conducting, Phil mistakenly believes Cathy is the final try-out and brusquely orders her to sing the music she has just delivered. Taking the chance, Cathy gives a rousing rendition of the tune, which impresses Phil and Frankie, who has stopped by. When Phil telephones Joe with his enthusiastic endorsement of Cathy, Joe has no idea who she is until she explains. Amazed but pleased that the studio's new messenger is also a wonderful singer, Phil and Joe arrange to have Cathy perform for producer Sidney Gordon the next day. That evening Cathy confides in Tobey, who is delighted by her surprise success. When Martha insists that Cathy remain at home to discuss further details of her charity event, Cathy refuses, having arranged a date with Phil. Phil escorts Cathy to the Embassy Club, where Frankie performs a nightly show. The following morning Martha, angered over Cathy ignoring her requested midnight curfew, insists that Elliot drive Cathy to work. Upon being dropped at the local library, Cathy accidentally leaves behind her wallet and Elliot discovers her studio identification card. Elliot reports his finding to a stunned Martha, and further reveals that Cathy has never worked at the library. Meanwhile at the studio, Cathy auditions with Frankie for Sidney, who is pleased and asks her to shoot a screen test. As Cathy is leaving the studio that afternoon, Tobey arrives to warn her of Martha's discovery. At home, Cathy faces Martha's anger, but insists that just because her own father was a failed vaudevillian does not mean show business is a disreputable profession. When Martha remains disapproving, Cathy moves out, but with nowhere to go, ends up at Phil's, who takes her to the studio boardinghouse. The next day while Cathy is shooting her screen test, Martha pays an unexpected visit to Joe. Later, Joe contacts Sidney to reveal that Cathy is underage and that Martha, her legal guardian, is refusing to allow Cathy to sign with the studio. At Phil's that afternoon, Cathy weeps bitterly over Martha's decision, but when Phil gallantly offers to marry her to allow her to legally make her own decisions, Cathy, although grateful, refuses. Later, Tobey contacts Cathy and Phil to reveal that Martha's charity is in desperate need of money and few tickets have been sold for the benefit. Tobey then asks Phil if he could convince Frankie and Billy Daniels to perform for Martha's benefit, which might soften Martha's attitude toward show people. Phil agrees and soon has arranged with Frankie to use the Embassy club for the benefit. Over the next few days, Tobey keeps the newspaper and TV ads of Frankie and Billy's scheduled appearance for the benefit from Martha. The night of the event, Martha is surprised and confused about being driven to the Embassy, but is quickly delighted by the crowd and enthusiastic reception. After Frankie performs and asks for support for the charity, he introduces Cathy. Martha is unexpectedly pleased with her granddaughter's display of talent and later, gives Cathy her blessing to sign with the studio as the co-star of Frankie's next film.
