In 1977, renowned paranormal investigators Ed and Lorraine Warren travel to the United Kingdom to assist the Hodgson family, who are experiencing poltergeist activity in their home in Enfield, a suburb of London. The family, particularly the second eldest of four children, Janet, is terrorized by what they believe to be the spirit of the previous owner, who insists that they leave his house. Upon their arrival, the Warrens are initially skeptical about the disturbances, attributing them to the children's imagination or fabricated for attention. However, as they dig deeper, they uncover a chilling connection to a demonic entity that poses a threat not just to the Hodgson family but to themselves as well.

As the Warrens try to help the Hodgsons, they also deal with Lorraine's recurring visions of a demonic nun, which adds a personal stake to their investigation. Lorraine fears that their involvement with this case might lead to a tragic outcome, reminiscent of a premonition she had earlier. The entity's malevolent intentions soon become evident, manifesting in violent and terrifying ways that push the Warrens to their limits. Their faith and expertise are tested as they confront not only the malevolent force haunting the Hodgsons but also the skepticism of the outside world, including the media and their own peers in the paranormal research field.