The story revolves around a young couple, Francis (played by Xavier Dolan) and Marie (played by Anne Dorval), who are expecting their first child. However, their joy is short-lived, as Marie begins to experience a mysterious and terrifying transformation. Her body starts to undergo a series of bizarre and unexplained physical changes, which seem to defy the laws of nature. As Francis tries to care for Marie, he becomes increasingly isolated and paranoid, unsure of what is happening to her or how to stop it.