The priest Philip Lamont discovers the existence of demons and begins to go the path of Merrin. He is also ordered by his superior to investigate his death four years ago, which happened, when he performed the exorcism of Regan McNeil in her former home.
In his quest he also visits Regan MacNeil (Linda Blair), whom Merrin exorcized and freed from the demon Pazuzu. She is still traumatized because of the event and therefore can only answer his question through hipnosis with the help of her tutor Sharon at the psychiatric center of Doctor Gene Tuskin.
During his investigation he discovers, that Pazuzu is determined of targeting her, like many others, because of her psychic healing abilities. He also discovers Kokumo, a child Merrin also exorcised. He has become a scientist, who fights plagues and gives him advice about how fighting evil.
In the meantime the demon targets Regan again. With the help of the priest, she faces him again at the former home of Regan, where the exorcism of Regan happened.
There, with the help of the priest, she finally manages to defeat him and end his evil activities.
- Linda Blair as Regan MacNeil
- Richard Burton as Father Philip Lamont
- Kitty Winn as Sharon Spencer
- Louise Fletcher as Dr. Gene Tuskin
- Max von Sydow as Pater Lancaster Merrin
- Paul Henreid as Kardinal
- James Earl Jones as Kokumo
Despite of the fact, that the movie was profitable, it was still a disappointment in comparison to the gross of the original movie. It also received negative criticism from the critics.