It follows a fading celebrity, Elisabeth Sparkle (Demi Moore) who, after being fired by her producer (Dennis Quaid) due to her age, uses a black market drug that creates a younger version of herself (Margaret Qualley) with unexpected side effects.

It made extensive use of prosthetic makeup designed by Pierre-Olivier Persin and primarily practical effects; these included suits, puppetry, dummies, insert shots, and approximately 21,000 liters (5,500 US gallons) of fake blood to portray Elisabeth's drug-induced transformation.

On her fiftieth birthday, Elisabeth Sparkle, a once-celebrated but now-faded Academy Award-winning Hollywood film star, is abruptly dismissed from her long-running aerobics TV show by the producer, Harvey, due to her age.

At the hospital, a young nurse covertly gives her a flash drive advertising "The Substance", a black market drug that promises a "younger, more beautiful, more perfect" version of oneself.

The new body, who names herself Sue, becomes an overnight sensation after auditioning to be Elisabeth's replacement and is eventually offered the chance by Harvey to host the network's prestigious New Year's Eve show.

Near the end of one weekly cycle, Sue parties and brings a man home for casual sex, delaying the switch by extracting additional stabilizer fluid, causing Elisabeth's right index finger to rapidly age.

[17] Fargeat spent several months in Los Angeles following the release of Revenge, and began writing the first scenes of The Substance at a coffee shop in Silver Lake[18] as a spec script; she became a producer to maintain creative control.

For example, colors were written into the script to symbolize character traits — Elisabeth Sparkle's yellow jacket representing a "superhero-like" quality before her transformation, and Sue's pink leotard signifying her femininity.

[30] The character Sue, described as blonde in a 2020 draft of the script,[41] was given her namesake to subconsciously evoke Lolita and Marilyn Monroe, "baby-doll"-like iconography, and classic beauty standards that continue to endure.

[45] She chose to have Elisabeth Sparkle host an aerobics class,[46] inspired by Jane Fonda's transition from a successful actress to her second career starring in exercise tapes.

[23] Fargeat had previously worked as a trainee assistant director[note 5] on the Moore-led film Passion of Mind (2000), handling tasks like making copies and bringing her coffee in the mornings.

[73] France was selected to accommodate the film's extensive shooting schedule due to practical effects work, with the country's 40% Tax Rebate for International Productions (TRIP) providing an additional incentive.

[36] Ultimately, he devised a simpler solution: two horizontal bicycle tires surrounded by LED tube lights, spinning together at the same speed around a stationary camera to create an infinity tunnel effect.

Fargeat decided to leave the rehearsal as well; Qualley instead chose to learn the moves in a private lesson, allowing her to practice in her hotel room and build confidence as she felt deeply ashamed by the whole series of events.

[106] The Substance required a three-month construction period to build the sets, including Elisabeth's apartment with distinct spaces like the bathroom and secret room as well as the New Year's Eve theater and a TV studio hallway.

[112] During the birth scene's point-of-view shot, two identical bathroom sets were built to simulate a mirror: Qualley acted in one, while Kračun (wearing a head-mounted camera) and a body double mimicked her movements in the other.

[119] Sue's wardrobe emphasized femininity, exposing her body, focusing on clichés associated with the male gaze including pink metallic colors, black Louboutin boots and a tennis skirt.

[128] When Elisabeth leaves to retrieve the substance, the sound design shifts from a noisy street to deserted suburbs with dogs, police sirens, and crows used to foreshadow danger.

[128] Inside the storage facility, sounds were shaped musically with metallic materials and sustained notes to give a feeling of discomfort, and then drawn back to only a low and clinical neon light.

"[101] Persin read the script, made a bid, and, while working on another project, sculpted a small plasticine[140] maquette of his design for the creature at the climax, "Monstro Elisasue"[note 8] over a few nights.

"[142][141] Fargeat deliberately sought to avoid making the effects look realistic, aiming instead to create a deformed representation of the aging process, shaped by the characters' fear and anger.

[152] Correcting it took a month[152] and temporarily halted the development of other prosthetics until the finger met Persin's desired standard of a balanced appearance, ensuring it would not look bulkier than the natural ones.

"[137] The crew were especially impressed when Moore decided to postpone filming one of her scenes until the next day after noticing that her prosthetics had deteriorated over several hours of earlier shots, as she felt it would be extremely disrespectful to their hard work.

[163] Persin drew inspiration from Niki de Saint Phalle, a French sculptor known for her vibrant and curvaceous figures (especially her depictions of female dancers);[137] artist Fernando Botero, whose sculptures often feature women with exaggerated proportions;[101] and David Cronenberg's The Fly.

The website's consensus reads: "Audaciously gross, wickedly clever, and possibly Demi Moore's finest hour, The Substance is a gasp-inducing feat from writer-director Coralie Fargeat.

"[211] Owen Gleiberman of Variety praised the film's director: "Coralie Fargeat works with the flair of a grindhouse Kubrick in a weirdly fun, cathartically grotesque fusion of Dr. Jekyll and Mr. Hyde and Showgirls.

"[214] Javier Ocaña of El País wrote that the film "is not that great", partly "because subtlety is not Fargeat's greatest virtue", but "mostly because the first 45 minutes seem like a covert remake" of John Frankenheimer's [superior] Seconds.

[215] Many filmmakers, including Ana Lily Amirpour, Edward Berger, Davy Chou, Kelly Fremon Craig, Robert Eggers, Adam Elliot, Hannah Fidell, Michael Gracey, Kitty Green, Laurel Parmet and Juel Taylor cited it as among their favorite films of 2024.

[216] Wendy Ide of The Guardian praised The Substance for its feminist perspective of older women, making note of how other female-led horror films like Carrie or Rosemary's Baby centre on themes of menstruation and childbirth.

"[217] The New York Times critic Alissa Wilkinson described the film as an exploration of the male gaze, noting the satirically exaggerated camera angles and shots, depicting the female characters in a way "that feels reminiscent mostly of porn".