In the town of Blissfield, a mystical and ancient dagger causes the lives of two diametrically opposite individuals to collide in an unexpected way. Millie, a meek, high school teenager, struggles with typical adolescent challenges, including bullies and an overbearing mother, while dealing with the painful absence of her deceased father. Her life takes a dramatic turn during the town's Homecoming festivities when she becomes the target of a local serial killer known as the Blissfield Butcher, a towering and brutal figure who has been terrorizing the community.

During a fateful encounter with Millie, the Blissfield Butcher wields the cursed dagger and stabs her, unwittingly triggering a mystical enchantment. The following morning, both awaken to discover that they have swapped bodies. Millie, now in the form of the middle-aged man, scrambles to make her friends recognize her true identity, while the Butcher utilizes Millie's appearance to blend into high school unnoticed, continuing his murderous spree. With time running out and the body switch set to become permanent, Millie must adapt to her imposing new physique, overcome the killer's instincts within her, and figure out how to reverse the curse before it's too late.