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.