Drama. Starring Brendan Gleeson, Chris O'Dowd and Kelly Reilly. Directed by John Michael McDonagh. (R. 100 minutes.)

"Calvary" is one of the smartest and most impassioned films about Christianity in recent memory, though to say that might give the wrong impression. In tone and strategy, the film is low-key and subtle; and the story can be appreciated both for its surface qualities and its deeper intentions.

With no preamble, writer-director John Martin McDonagh lays out the basic situation: Father James (Brendan Gleeson) is hearing confessions one day when a voice on the other side of the grate tells him a couple of very disturbing things. The first thing the man tells him is that, as a child, he was repeatedly abused by an evil priest, now deceased. The second is that he plans to kill Father James in exactly one week.

He knows Father James is completely innocent of this crime, that he's a good, hard-working priest, but that's the idea. He wants to do something horrible and irrational in revenge against the universe for the horrible, irrational thing that was done to him.

This is a compelling setup, one that easily might distract the casual viewer from realizing the biblical parallel, of an innocent person being asked to die for the sins of the guilty. In any case, McDonagh doesn't lose himself in metaphor, and despite the film's title, which refers to the place where Jesus was crucified, the movie is not about establishing rigid connections. Rather it's about exploring the challenges of living a Christian life, the not-pretty, hands-on difficulty of practicing forgiveness and forbearance, which always seems a lot easier when you're talking about 2,000 years ago.

The movie's success lies in the fact that Father James is no Christ figure, but a specific and realized character trying to do the right thing. A priest in a small Irish village, he carries an awareness of his own imperfection in his very manner, and the movie makes clear that he's had to wrestle with himself. A widower who was called to the priesthood in midlife, he has a devoted but troubled adult daughter (Kelly Reilly) and a history of battling the familiar Irish demon, alcohol.

Speaking of demons, many supernatural films deal in demon possession, and they couldn't scare anybody. But "Calvary," if not outright frightening, is genuinely alarming in its subtle hint of something terribly wrong within the town. I imagine most people will watch the film and merely see the village as populated by vivid eccentrics. But a closer look at these odd, bitter, hostile characters will suggest something darker at work.

Indeed, the bulk of the movie consists of a series of bizarre encounters between Father James and the villagers, who taunt him and challenge his faith and carry on in outlandish ways that barely conceal their misery. Whether you choose to see them as metaphorically or literally demon-possessed, McDonagh's intention is clearly along these lines.

A sense of gradually escalating weirdness maintains the movie's sense of forward motion, and that - plus Gleeson's scruffy humanity, used to loving effect - is quite enough for "Calvary" to hold the audience in its grip. Also look for Marie-Josee Croze, in the small and yet strangely key role of a woman transfigured by grief.