The film is the second attempt at showing Father Merrin's early life and his first battle with Pazuzu many years before he meets Reagan in The Exorcist.
The film begins with Father Merrin in his hometown of Holland during WWII as a priest. He is forced to perform an act that haunts him for years and as a result loses his faith. Fast forward several years and Merrin is now in Kenya working on an archaeological dig. Workers dig up a church buried under the sand that was extremely old. As they open up the church and start to explore it, strange things start to happen and an evil is unleashed that will put Father Merrin's faith to the test.
Uniqueness in Film Industry
While neither this nor Exorcist: The Beginning did well at the box office, they offered something that has probably never (or rarely) done in Hollywood: two director's take on the same script material.
There were some differences between the two films, but the main story was kept the same: we get to see Father Merrin's early life and his fall and rise from faith in the church.
While Hollywood has done remakes and/or reboots of movies before, this was very different. Paul Schrader filmed this and it ended being more of a psychological thriller. The studio was not impressed with this and wanted something with more action so they scrapped Schrader's film and went with Renny Harlin, a new script writer, and a few different actors for certain roles. This is what they went with and released as Exorcist: The Beginning. The film bombed at the box office and so the studio decided to release Schrader's version the next year in a limited release. The film didn't make much money either and both were panned widely by critics though Roger Ebert gave Dominon four stars.