The narrative unfolds through three defined demonological phases: Infestation, Oppression, and Possession.
1. Infestation: The Perrons unwittingly trigger dormant entities upon discovering the boarded-up cellar. Spirits torment the daughters by pulling their legs at night, slamming doors, and communicating through the spirit music box.
2. Oppression: The primary entity targets Carolyn as the emotional core of the household, inflicting foul smells, bruising, and psychological isolation. Lorraine uncovers historical records showing that in 1863, the land belonged to Bathsheba Sherman—a relative of Mary Towne Eastey (hanged in the Salem witch trials). Bathsheba sacrificed her seven-day-old infant to Satan and hanged herself from the yard's large tree, placing a curse on anyone who would take her land.
3. Possession & Climax: After the Warrens document evidence for the Church, Carolyn becomes fully possessed by Bathsheba. She abducts her daughters Christine and April and returns to the farmhouse cellar with shears to complete the sacrifice. Because Catholic Church authorization for an exorcism will take too long, Ed performs an emergency exorcism himself while Roger, Lorraine, and assistants physically restrain Carolyn.
4. Resolution: Bathsheba forces Carolyn to break free and target young April under the floorboards. Lorraine appeals directly to Carolyn’s maternal love, reminding her of a family day at the beach. Anchored by the memory, Carolyn regains her agency, rejects the entity, and allows Ed to finish the exorcism rite, banishing Bathsheba back to Hell.