New York Harbour: Welcome aboard the Ile de France, a cruise ship set for Europe. At the pier, we meet Lorelei Lee and her friend Dorothy – two former showgirls who are eagerly awaiting Lorelei’s fiancé Gus, the wealthy son of a button manufacturer. Their wedding is to take place in Paris, but Gus shows up only to cancel the trip: his father, who is worried about the invention of the zipper, has summoned Gus to stay. The two women set sails without Gus and attract attention aboard. While Dorothy enjoys the company of a squad of Olympic athletes, Lorelei inspects her fellow passengers: there is wealthy Mrs. Spofford, whose son Henry watches over her drinking habit. Then there is Lady Beekman, an English aristocrat on the lookout for a potential buyer for her diamond tiara. Her husband, on the other hand, only has eyes for all that is young and female, Lorelei included. A telegram from Gus arrives. To Lorelei’s alarm, he seems to have found out about some dubious details from her past. Following Dorothy’s inquiry, Lorelei reveals that she grew up on “the wrong side of the tracks” in Arkansas. As a young typist, she experienced sexual violence by her boss and shot him in self-defence. Convinced that Gus has ended their engagement, Lorelei vows to find a new husband. The candidates’ most important criteria: wealth! Dorothy on the other hand will marry for love alone. Unsurprisingly, she is startled when finding herself attracted to Henry Spofford, who doesn’t seem to fit her ideals. Lorelei too has made her choice: Josephus Gage, an entrepreneur with a zipper factory – of all things! Enter Gus, who has decided to come in person after Lorelei left his numerous telegrams – a renewed proposal included – unopened and unanswered. Meanwhile, Lorelei is being confronted by Lady Beekman’s solicitor, who accuses her of theft: She is said to have borrowed money from Sir Beekman to get hold of the tiara. Gus finds Lorelei surrounded by men and announces their breakup.
A French-themed party is in full swing at the cruise ship’s own nightclub. Lorelei attends with Gage, and Gus takes his revenge by introducing revue dancer Gloria. Enraged, Lorelei must conclude: men are fickle, and romantic gesture all but worthless. If you want to enjoy a financially secure life, diamonds are a girl’s best friend! Finally, Lorelei and Gus confide in each other. Upon hearing Lorelei’s life story, Gus is ready to marry her on the spot, but she insists that Esmond senior give his consent first. After several days of waiting, Gus’ father arrives. He is aghast when Lorelei presents him with a business deal: she consolidated the button and zipper factories – leaving everyone a winner. Naturally, Esmond senior approves of the idea, and of the wedding plans. Dorothy too can finally commit to Henry, when finding out that Mrs. Spofford owns all of the family’s assets – with no plans to hand them over to her son. It’s a happy end for all!