The Substance's ending is a tragic conclusion to a wild body horror comedy, underscoring the film's views about self-worth and self-destruction in the entertainment industry. The film focuses on the titular "Substance," a mysterious serum and medical by which someone can create a younger copy of themselves. This allows them to spend a week in a "perfect" body for every week in their normal form, although there are strict rules about how to maintain the process. The Substance's lead characters are two sides of the same person, aging star Elisabeth and her younger self, who dubs herself Sue.

The film is a dark comedy about the entertainment industry, but it's also quietly a tragic horror story about the lengths Elisabeth and Sue will go to achieve their ambitions, even at the cost to themselves. Steadily seeing each other as rivals for their shared time, the two sides of Elisabeth ultimately set up their own undoing. The themes of Demi Moore's arc in The Substance elevate the body horror comedy and add a personal level of tragedy and gravitas to the story. Here's how the ending of The Substance highlights the thematic core of the film.