During a Sun Valley vacation, a woman tries to solve her roommate's romantic problems only to get caught in a love triangle of her own.
Christine Riverton Duncan, the star of the "Melody in Springtime" water ballet, shares her Chicago apartment with Ellen Hallet, a secretary to playboy railroad tycoon Douglas J. Morrissen, Jr.. One evening, while dining at a nightclub with the boring Linda Kinston, Douglas pretends that Ellen is his fiancée to scare off his date. Ellen, who is in love with Douglas, gladly plays the part, and then stays for a drink. At the end of the evening, Ellen returns home drunk and depressed, certain that Douglas does not love her. The following day, Ellen accepts an invitation to join Douglas on a business trip to Sun Valley. Elated, Ellen telephones the news to Christine, who advises her to run out and buy a dress with a "low, wicked neck line." No sooner does Ellen bring home a new dress, than Douglas calls to cancel his invitation. Fed up with Douglas' habit of only calling on Ellen when he needs her help to fend off other women, Christine decides to help her roommate by playing a hoax on Douglas. After boarding Douglas' train to Sun Valley, Christine wins the playboy's affections and then surprises him with hints that she expects marriage. In Sun Valley, complications arise when Christine falls in love with hotel bandleader Dick Layn. Soon after Douglas returns to his office, Ellen bumps her head on her desk and is briefly knocked unconscious. While attending to Ellen's injury, Douglas finally notices her beautiful eyes and invites her to dine with him. Ellen prepares a romantic dinner for Douglas at her apartment, but she begins to lose hope in winning Douglas when he tells her that he will be returning to Sun Valley to resume his romance with a woman he met there. Back in Sun Valley, Christine wins the title of "Duchess of Idaho" in a dance contest, and is about to be proposed to by Dick, when she is distracted by the Douglas' arrival. Dick misinterprets Christine's sudden change in behavior as a rejection, but Christine eventually resumes her romance with Dick when Douglas tells her that he is in love with Ellen. Meanwhile, Ellen, believing that Christine has stolen her man, goes to Sun Valley to straighten matters out. Following a series of misadventures in Sun Valley, the two women lose their men and return to Chicago. A short time later, Dick and Douglas pay an unexpected visit to Ellen and Christine at their apartment, hoping to reconcile with their sweethearts. Ellen immediately rushes into Douglas' arms, and after Christine explains the ruse to Dick, he takes her back with open arms.
