Exorcism movies are to the general run of horror pictures what gangster movies are to crime films. They are related to the larger group, but their pay-off is different. Exorcism movies please their audience with ritual and with the larger significance of their issues.

A new Russell Crowe movie, “The Pope’s Exorcist,” is a worthy inclusion to the list of films about priests flushing demons from humans they have possessed. It also stars Franco Nero, Vanessa Redgrave’s husband and the star of the original “Django” (1966). Nero plays the ailing pope.

At the beginning of the new movie, he is protecting the office of Pope’s Exorcist and its incumbent, the quirky Father Amorth (Crowe) from a reform panel that questions the need for exorcism. The movie is, by the way, based on memoirs by the real life Father Amorth.

But the first thing the audience sees here is Amorth at work in a humble Italian house. The adult son is apparently possessed. He is writhing on a bed, cursing all comers in a creaky voice. Amorth takes out his demon-revealing medallion and holds it up in the face of the man. The priest checks the guy’s eyes.

Then he engages his subject in a verbal exchange, and an assistant brings a pig into the room. Amorth asks the man if he can possess other bodies? Even a pig’s? When he avers, the assistant waits a beat for the demon spirit to go to the pig, then shoots the animal in the head. Problem solved.

You see, the man wasn’t actually possessed. This is what the exorcist found out with his medal. So the case was a psychological one, not a spiritual one. The man only thought he was possess, and the priest gave him a psychological excuse to give up the delusion.

Back in Rome, the reform panel calls Amorth in to remonstrate with him for having performed an exorcism without official permission. He explains that he performed no rite. And then he rides off, the now bulky Crowe on a Vespa motor scooter, to kid some young nuns at the Vatican.

The bulk of the story, though, is about a more serious case. Amorth is sent to Spain where a boy who saw his father impaled in a car wreck has stopped speaking. And now, living in what was, years ago, an abbey, he is showing signs of demonic possession. Here Amorth is helped by the local priest.

The medal test shows the demon present. The powerful demon, the Pope himself discovers in research, is a priest gone bad 500 years before. He was a leader of the Spanish Inquisition, a historical church operation that used torture to establish a homogeneity of religion in the newly united nation and that helped to fight off the influences of the protestant reformation.

When elite insiders go bad, they can cause substantial trouble. This abbey became one of half a hundred covert devil worship centers inside the church. With the boy’s arrival, the old evil spirits have come out from under the church’s seal. Now Amorth is fighting not just to save the boy but also to save his family members and to stop this demon from using his leverage against the church in general.

We see the rituals the priests use, and the attempts at possessing the boy’s mother and sister. The abbey (apparently actually Irish) is a terrific setting. It’s essential spookiness feeds the story’s suspense. Incidents. Characters from the priests’ lives appear in flashback. And everything builds to a satisfactory climax.

The only thing is, this isn’t a horror movie. It isn’t always trying to catch viewers unaware. Luckily, audience members seem to understand this before they step into the theater.