When Penelope "Penny" Craig sees that her sister Kay is in love with Richard Watkins, to whom their sister Joan has become engaged, she devises a plan to find another man for Kay. Penny, who is studying to be an opera singer, asks pianist Harry Loren to dinner, but when he shows more interest in Joan than Kay, Penny insults him and throws him out, much to the horror of her mother and sisters. Convinced that Penny was displaying jealousy and therefore, is in love with an older man, Mrs. Craig decides that the best solution is to keep her from seeing Harry at the music school, and asks her husband Judson, who is completely distracted by his work as a stockbroker, to tell Penny that her voice is going bad and she must discontinue her singing lessons. Penny is devastated by this news, but then realizes that the best way to solve the situation is for Harry and Joan to fall in love, thereby leaving Kay and Richard to get together. When Richard takes the sisters out for a diversion, Penny asks him to take them to Club 33, where Harry plays piano. Harry dances with Joan and tells her of his plans to move to Australia, where he has been offered a job. Meanwhile, Penny embarrasses Kay by telling Richard about her affection for him, and Kay slaps Penny. Back home, both sisters believe that all of Penny's actions have been selfish, and Penny is so offended she refuses to talk to Kay. The day before Joan's wedding, Penny goes to her father's office, and after interrupting an important meeting, bursts into tears. Finally realizing that his daughter is desperately unhappy, Judson takes time out of his day to console Penny, who reveals to him the source of all her recent behavior. Judson promises to set everything right. True to his word, the next day, Judson leads Joan out of the ceremony and into the arms of Harry, and then leads Kay to the altar with Richard, while Penny beams with happiness.