Throughout the film, the Campbell family, led by Sara (played by Virginia Madsen) and Peter (played by Martin Donovan), moves into a new house in Connecticut to be closer to the hospital where their son, Matt (played by Kyle Gallner), is receiving treatment for cancer. They soon discover that the house has a dark past and is haunted by malevolent spirits.
As the hauntings escalate, the family seeks help from a local priest, Reverend Nicholas Popescu (played by Elias Koteas), who performs an exorcism to cleanse the house of its evil presence. However, the exorcism fails, and the family’s ordeal continues to worsen.
In the climax of the film, Matt discovers the truth about the house’s dark history and the connection to a mortician named Jonah (played by John Churchill), who performed gruesome experiments on the deceased in the house’s basement. Matt realizes that he has a psychic connection to Jonah, allowing him to see the spirits that haunt the house.
As the spirits grow more aggressive, Matt confronts Jonah’s ghost in the basement, seeking to uncover the truth behind the haunting. In a terrifying showdown, Matt confronts Jonah’s vengeful spirit and learns that he must put an end to the evil plaguing the house once and for all.
With the help of his family, Matt performs a ritual to banish Jonah’s spirit from the house, sacrificing himself in the process to save his loved ones. The ritual succeeds in purging the house of its malevolent presence, but at the cost of Matt’s life.
In the aftermath, the Campbell family mourns the loss of Matt but finds solace in the knowledge that he sacrificed himself to protect them from the evil spirits haunting the house. They leave the house behind, hoping to move on from the traumatic events they experienced there.
The film ends with a sense of closure as the Campbell family drives away from the haunted house, leaving the horrors of their past behind them. However, the haunting experiences they endured will stay with them forever, serving as a reminder of the darkness that lurks in the shadows.