As a favor to a friend, policeman Tom O'Meara (Harrison Ford) lets visiting Irishman Rory Devaney (Brad Pitt) stay with him and his family in New York City. Rory's visit is quiet at first, but when Tom and his wife, Sheila (Margaret Colin), return home one day, they're accosted by intruders. Tom soon realizes that Rory is in the Irish Republican Army. When it becomes clear that Rory's stateside trip is part of an effort to transport illegal guns to Dublin, Tom is compelled to stop him. The Devil's Own / Film synopsis
The movie seems to be about Isabella Rossi's quest to figure out exactly what happened to her mother during a botched 1989 exorcism that left three clergy dead and her mother committed to an institution in Rome.
This trope traces its origins to the legend of Faust, a scholar who, driven by dissatisfaction and ambition, makes a pact with Mephistopheles (the Devil), trading his soul for unrestricted knowledge and worldly pleasures.
Well-meaning people make deals with the devil because of a few possible reasons: (1) they don't know or assume good intent, (2) feel they don't have a choice, (3) they are tempted by the upside, (4) they think the devil's changed or they can transform the devil, (5) they think they can out-devil the devil.
A 'Deal with the Devil' is a narrative trope where a character makes a pact with the Devil or a demonic figure in exchange for worldly desires like wealth, power, knowledge, fame, or other personal gains.
Understood as the embodiment of evil, a figure of temptation, and a potential foil to God, the Devil works as a complex ethical symbol.
Metaphor. The term "a deal with the Devil" (or "Faustian bargain") is also used metaphorically to condemn a person or persons perceived as having cooperated with an evil person or organization. An example of this is the Nazi-Jewish negotiations during The Holocaust, both positively and negatively.
Dealing with the Devil: Professor Explores Contracts with the Prince of Darkness in Popular Culture. In the story of Faust — which has been reinterpreted numerous times in plays, movies, books and music — the protagonist sells his soul to the devil, often in exchange for knowledge or power.