Keanu Reeves acts as an exorcist and freelance occult consultant in this movie. I'm not a huge fan of Keanu, though his work isn't offensive and he has many solid movies under his belt. This is one of them.
The only thing worth knowing about the occult is that while we are programmed to scoff at it, the higher up the food chain a person climbs the more likely, no, the more unavoidable it is.