Lawyer Irene (Laura Linney) received a lawsuit. A priest used religious means-exorcism rituals to treat the girl Emily's serious illness, which delayed Emily's correct medication time. In court, a battle between religion and science began. The beginning of the incident originated from the horrific experience of 19-year-old female college student Emily (Jennifer Carpenter). When she was sleeping in the university dormitory, she felt that a supernatural demon was invading, and then more terrifying things happened one after another. Emily was out of character. She became black-eyed and behaved strangely. She lived in a nightmare of hesitation and demons all day long. Emily could not control her will and was in pain. The family found a psychiatrist for her, but there was no improvement. In desperation, the priest (Tom Wilkinson) was invited to find out, only to learn that Emily was possessed by the six ancient demons. She was haunted by all the demons, and she could only escape through religious rituals to exorcise the demons. The priest's exorcism did not save Emily, but led to her being accused. However, atheists believed that demon possession was nonsense.