Richard Jacks (Tim Daly) is a perfumer working at a major fragrance company. His projects have failed and the chief executive Mrs. Unterveldt (Polly Bergen) is thinking of replacing him with a woman. After his great-grandfather dies, Jacks attends the will reading. He receives nothing but notes from scientific experiments. He discovers that his ancestor was Dr. Henry Jekyll. Jacks attempts to refine Jekyll's formula. He decides to add more estrogen to the mixture in the hope that it will prove less dangerous.
Monitoring his vital stats after ingesting the formula, he gives up and attends a job interview. Although everything appears normal at first, his voice begins to crack, his nails grow longer, and the hairs on his arms recede into his skin. Jacks then feels a strange sensation in his groin area and watches in horror as his manhood disappears. Jacks tries to leave, but starts to develop breasts. Embarrassed, Jacks flees back to the lab, leaving his interviewer speechless. Back in his office, the final stages of the transformation into a woman take place.
The new female alter-ego names herself Helen Hyde (Sean Young) and introduces herself as Jacks's new assistant. Helen rewrites his reports, is kind to his secretary, flirts with his superiors, Yves Dubois (Harvey Feinstein) and Oliver Mintz (Stephen Tobolowsky) and rewards herself with a shopping spree. Later Helen meets and befriends Jacks' fiancee, Sarah (Lysette Anthony), but has Sarah move out of Jacks' apartment so she can have it for herself.
The next day, after several comments from colleagues, Jacks realizes that Helen was real but is unable to access any of her memories. Nonetheless, he feels invigorated and invites Sarah to his place for a romantic meal. Everything appears to be going well until he realizes he is again transforming into Helen, causing Sarah to flee. Hyde becomes resentful at having to share a body. She disfigures one of Richard's colleagues, Pete (Jeremy Piven), and steals his ideas. She even attempts to seduce Oliver. Just when Hyde is about to have sex with Oliver, she starts changing back into Jacks and hides in the bathroom and escapes via a nearby window.
Due to her flirting with Oliver, Hyde is named Jacks' superior at work. To stop her, Jacks handcuffs himself to the bed, only to be horrified as Sarah walks in and finds his closet to be full of lingerie. This leads Sarah to believe that he and Hyde are having an affair. Hyde then has a private meeting with Dubois and Mintz presenting her perfume, where She fondles Dubois' groin and Mintz' crotch with her hosed feet simultaneously under the table, thus persuading them. She then sleeps with Dubois as he confronts her about her false resume.
Hyde then warns Jacks via video of her intentions to take over completely. He then realizes that he is actually starting to spend more time as Hyde than himself and that he has to come up with a plan before he disappears completely. Jacks tries to humiliate Hyde in front of her superiors by stripping naked and writing obscenities all over his body, hoping that they will walk in on her after she takes over. Hyde manages to outsmart him by delaying the change, causing his plan to backfire and Jacks to be fired.
Sarah is finally convinced by seeing CCTV footage from the initial transformation. Jacks comes up with a formula that would effectively destroy the Hyde part of himself, but he must consume it as Hyde within a certain time frame. After he transforms, Sarah attempts to inject her with the formula but fails—injecting only about 20% of it, causing random body parts to spontaneously transform between male and female. A fire breaks out in the apartment and Hyde escapes.
At the launch of "Indulge", the perfume she stole from Richard, (the one that Mintz and Dubois sniffed as she fondled them with her feet), Hyde steals a guest's dress. As she mingles, the effects of the formula cause her to temporarily grow stubble; her breasts also disappear and reappear. Sarah, who sneaked into the party, hides in a podium and waits until the promotion video starts before injecting the rest of the formula into Hyde, who begins transforming back into Jacks for good. A relieved Jacks realizes it's over but sees that he's now standing in a room full of colleagues wearing a dress. He makes a speech about the only way he could understand a woman was to become one. He then is offered a promotion as well as a vacation, which he accepts. As he removes the undergarments he comments "Helen and her damn thongs".Tim Daly as Dr. Richard Jacks whose only wish is to make a scientific breakthrough that will change his life for the better.Sean Young as Helen Hyde, a nymphomaniac seductress with a quest for power.Lysette Anthony as Sarah Carver, Jacks's devoted girlfriend.Stephen Tobolowsky as Oliver Mintz, Jacks's supervisor.Harvey Fierstein as Yves DuBois, a marketing mogul.Thea Vidale as Valerie, Jacks's overworked and disgruntled secretary.Jeremy Piven as Pete Walston, Jacks's colleague.Polly Bergen as Mrs. Unterveldt, the company's CEO.
The film received a 14% "rotten" rating on Rotten Tomatoes.
The film was nominated for three Razzie Awards including Worst Actress for Sean Young, Worst Remake or Sequel and Worst Screen Couple for Daly and Young.
"At an age when she should be hitting her stride," wrote film critic Mick LaSalle, "she is already parodying herself -- parodying her public image, of all things, not her screen image...It's just possible that schlock is Young's natural element and roles like this her true calling". Hugo Davenport in the Daily Telegraph said, "Apart from being a travesty of Stevenson, it is so crass, witless and misogynistic that it makes "Confessions of a Window Cleaner" look like Dostoevsky".
A review from The Austin Chronicle summarized the film by saying, "Overall, this PG-13 bore is neither crass enough nor intelligent enough to hold anyone's attention."
After its theatrical run, HBO released the film onto VHS and Laserdisc, then in 2004 onto DVD.