Patricia Foster, [Doris Day], an industrial designer for Femina Cosmetics, owned by Sir Jason Fox [Edward Mulhare], is arrested for trying to sell a secret deodorant formula. She is fired from Femina and hired by Matthew Cutter [Jack Kruschen], the head of rival May Fortune. This is actually a scheme devised by Sir Jason Fox [Edward Mulhare] to steal the formula for a new water-repellent hairspray, invented by Dr Stuart Clancy [Ray Walston], May Fortune’s chief cosmetic chemist.
Christopher White [Richard Harris], Cutter’s right-hand man, tells Patricia that he, too, secretly works for Sir Jason. Patricia visits the apartment of Su Ling [Irene Tsu], Clancy’s secretary, and finds her unconscious on the floor. She takes a sample of the powder lying on the table and pockets a bottle of the hairspray. Christopher catches Patricia and threatens to tell Sir Jason that her real name is Felippa Fowler; he reveals that he is actually working for the CIA.
Patricia is the daughter of Robert Fowler, an Interpol agent who was murdered while skiing in Switzerland on the trail of a narcotics ring. She learns the hairspray bottle is a pricey Swiss product not used by Cutter. Christopher says that Clancy has Swiss connections—he was married to a Swiss woman and has children living in Switzerland, and he was also a competitive skier.
Patricia travels to Switzerland and seeks out Madame Piasco [Lilia Skala], Clancy’s mother-in-law and the true inventor of the formula. Madame Piasco gives Patricia a bottle for free, explaining that May Fortune now has distribution rights and it will soon reach the American market.
On the same hill where Robert died, Patricia goes skiing and comes under fire from a masked skier. A helicopter arrives and Christopher rescues her. Patricia realizes that neither Christopher nor Sir Jason were ever after the hairspray; Clancy, once Sir Jason’s chief chemist, was a failure, and Sir Jason’s real aim is to uncover the mastermind behind Clancy’s work, whom he still cannot identify. Despite this, Patricia plans to deliver the hairspray to Sir Jason, a mission she had agreed to. Christopher and Patricia declare their love, though he asks for one more assignment related to Sir Jason.
Later, Christopher secretly records Patricia while she speaks to Clancy. She offers Clancy a job as Femina’s head chemist with an illicit bonus, but Clancy declines, noting that Cutter already knows about Piasco and that he is content where he is. Back in Cutter’s Paris office, Cutter watches the footage and tells Christopher that it could ruin Sir Jason.
Patricia visits Sir Jason, who claims he convinced Piasco to work for him. She finds this hard to believe and notes the discussion about the analysis of the black powder, which contains a narcotic. Patricia had already had the powder analyzed herself; this other analysis was a test to press someone into telling the truth or to implicate him in Robert’s murder. Sir Jason reveals that Cutter sent the film to the police, who are now pursuing Patricia for bribery.
As the police close in, Christopher whisks Patricia away. He admits that he works for Interpol. Patricia informs Interpol that the narcotics were smuggled as May Fortune face powder, which was harmless until incinerated, when it turned into a hallucinogen. The police are skeptical that Cutter could head a narcotics ring.
Donning a microphone for Interpol while probing Cutter’s Paris office, Patricia tells a cleaning lady that she need not tidy there. The cleaning lady turns out to be Clancy in disguise, armed with a gun—he was Robert’s killer. Patricia fights Clancy, who is shot and dies. Sir Jason arrives with a gun, determined to seize control of the cosmetics market. With Clancy dead, he forces Patricia into a helicopter and takes off. Christopher shoots him, and Patricia flies the helicopter back to Paris, landing atop the Eiffel Tower. Patricia and Christopher end the film together.
