In a quiet neighborhood of Georgetown, a single mother, Chris MacNeil, faces the harrowing transformation of her 12-year-old daughter, Regan. What begins as a simple case of childhood tricks and strange behaviors quickly turns into a terrifying nightmare when Regan starts showing signs of demonic possession. Her behavior becomes erratic and violent, and soon, doctors are baffled by her sudden physical and mental deterioration.
Desperate for answers, Chris seeks help from the clergy, bringing her case to a priest who is experiencing a crisis of faith, Father Karras. This priest has been struggling with the death of his mother and his own disbelief in the power of evil. As the supernatural manifestations in Regan escalate in intensity—from profane language to unimaginable levitations—Karras is forced to confront his own doubts while investigating the phenomenon.
Eventually, Karras requests permission to perform an exorcism, an act that will push him to the brink of madness and test both his faith and his life. The climactic struggle between good and evil unfolds in a visceral and heart-wrenching battle, revealing not only the sinister force that has possessed the girl, but also the redemptive power of faith itself. As horror is unleashed, the boundaries of sanity are challenged in this unsettling exploration of the deepest terror.