The Reverend Edward Siebert’s journey with “The Pope’s Exorcist,” a movie about the Catholic Church’s most famous exorcist, started with a trip to Milan six years ago. The Jesuit priest says he was sitting at a restaurant drinking wine and contemplating an airline ticket he had bought a day earlier. He was also concerned about the deal he had recently closed with the Society of St. Paul to buy the rights to the life story of the Reverend Gabriele Amorth, the late Pauline priest known as “the James Bond of exorcists.”

Siebert, who teaches film at Loyola Marymount University in Los Angeles and maintains the school’s film production company, didn’t have any motion picture credits to his name and, at the time, wondered, “What have I gone and done?” Today, he breathes a sigh of relief as an adaptation of Amorth’s life unfolds on the big screen as “The Pope’s Exorcist,” starring Rusell Crowe in the titular role, opened in theatres earlier this month.

In 1986, Amorth was appointed chief exorcist of the Diocese of Rome and stayed there until 2016, when he died at 91. During his time, he claimed to have done more than 60,000 exorcisms. The first of his books, “An Exorcist Tells His Story,” was released in 1990, becoming an instant bestseller and translated into over 30 languages. Amorth named “The Exorcist” his favorite movie that same year and founded the International Association of Exorcists.

Siebert, also one of the film’s executive producers, says he was a doubtful candidate to do this project. However, he said Michael Patrick Kaczmarek, a New Mexico-based filmmaker he worked with, persuaded him with the power of Amorth’s stories. According to Kaczmarek, in 2015, he reached out to Amorth through his religious order’s publishing company. The executives told him many people tried to get the film and production rights for the exorcist’s books but were always denied. Still, Kaczmarek’s persistence paid off.

Kaczmarek said, “Through the use of translators, I sent Father Amorth detailed correspondence where I assured him of my religious devotion and sincere desire to respect his exorcism ministry.” He added that his team effort with Siebert helped sway Amorth of his intent to uphold the story’s religious integrity. Siebert said Amorth’s stories scared him initially, but he was moved by the priest’s faith and willpower to help people. Amorth said 98 percent of the people who asked for his help needed a psychiatrist, not an exorcist, a detail Crowe’s character clarifies in the movie.

Like Siebert, Crowe has also admitted that he’s not a horror movie fan during various media interviews because he prefers “to sleep deeply at night.” However, he said Amorth’s character intrigued him. He read the priest’s first two books and spoke with people who watched him perform exorcisms. Crowe said two attributes of Amorth’s character reeled him in, his “unshakable purity of faith and his wicked sense of humor.”

In “The Pope’s Exorcist,” set in 1987, Crowe’s Amorth goes to Spain with his apprentice to investigate a young boy’s possession. In Spain, he uncovers a “centuries-old conspiracy” the Vatican attempted to cover up. “The Pope’s Exorcist” is currently in theatres.