RALPH SARCHIE, retiring from the New York Police Department after close encounters with cases of demon possession, became an exorcist. The film Deliver Us from Evil (Cert. 15) now on release is - in words even bigger than the title - "inspired by the actual accounts of an NYPD sergeant".

The film quickly starts to give us the equivalent of a white-knuckle ride. And a very good one it is, because it doesn't solely rely on horror to get us through almost two hours' examination of the mystery of evil. The director, Scott Derrickson, has been this way before. Included in his past films is The Exorcism of Emily Rose (Arts, 25 November 2005) where a (real-life) priest is tried for homicide after a botched ministry of deliverance. Deliverance is also at the heart of this new film, but who is its primary target? As the piece progresses, we come to realise that it's Sarchie himself.

Eric Bana plays this gritty Bronx cop beset by everyday demons of cruelty, vice, and downright wickedness: crazy people doing horrible things, a baby left to die down a side street, domestic violence, etc. All is enough to make him, an erstwhile Roman Catholic, a Manichaean figure, convinced that his beat (and therefore the world) is incapable of goodness. When it becomes clear that a number of unpleasant incidents are all connected to one man's wall-painting, Sarchie comes to believe that the artist is demonically possessed.

The Church, in the form of Fr Mendoza (Édgar Ramírez), has already discerned this. And, while there are all the thrills and spills you would expect of a Jerry Bruckheimer production, the heart of the story is Sarchie's slow return to faith. Demon-busting is relatively easy. Something wicked this way comes; therefore, attack it. But why, Sarchie asks of the priest, is a God-created world so wayward, so evil? Mendoza points the policeman in the direction of his own inner being and its struggle for goodness to prosper.

From what we know of the film's director, this work is something of a spiritual odyssey personally. Derrickson was brought up in a fundamentalist household, and, after much soul-searching, is now a devout Presbyterian. Where Bana's portrayal probably differs from the real-life demonologist is that it doesn't depend only on interpreting seemingly paranormal occurrences in the way Sarchie continues to do. The film's policeman undergoes a faith journey that is just as interesting as whatever causes all those things that go bump in the night.

WHEN a film includes a song titled "Act of the Apostle", someone named Eve who is juxtaposed with an apple tree, and an expressed conviction that all creativity comes from God, it isn't hard to guess that the director, Stuart Murdoch, has an interest in faith. His film God Help the Girl (Cert. 15) is less clunky a statement of belief than it sounds, and is presented - a rare genre nowadays - as a musical. That is mainly because it is based on a 2009 concept album by Murdoch's group Belle and Sebastian, whose songs are often infused with religious concerns.

Eve suffers from depression and an eating disorder. She is a girl in need of divine help. Interestingly, her therapist's name is Miss Browning (Cora Bissett), which feels an in-joke, because Eve is played by Emily Browning. The therapist asks Eve when she stopped feeling good about herself. "Till I moved away from home," she says, which was Australia.

Given the apple-tree image accompanying that remark, we're meant to read this as Eden, now a world away. Breaking into song, as she frequently does, she questions herself with "Is this your soul you're facing?". She happens upon James (Olly Alexander), a would-be musician, working as a lifeguard. "So you're always saving people?" she says. He goes about saving Eve by means of music.

They form a band with an acquaintance, Cassie (Hannah Murray), and are not overnight successes. We can't guarantee we'll ever be, James says. Only God can, and that will manifest itself whenever someone manages to write a classic song. This is, in effect, the same argument as the envious Salieri posits in Sir Peter Shaffer's Amadeus. While James goes off in the direction of church to take stock of his life, Eve (like Murdoch himself) finds Jesus with the help of a masseur's healing touch. But these faith experiences remain statements that are never explored.

One doesn't expect much realism in musicals - Eve, an impecunious student, wears more changes of clothing than Naomi Campbell and Kate Moss could muster on a combined fashion shoot - but at best they magnificently illustrate some deeper truths about ourselves. This film doesn't.

The songs, more choreographed than danced, are punctuated with myriad shots, making it reminiscent of pop videos rather than, despite its urban locations (Glasgow), the likes of West Side Story. These youngsters are having fun, even if much of the time we're not. It is also regrettable that the film starts with the words "I'm bored out of my mind." They are a hostage to fortune when critics are around.