In Catholicism there is a definite distinction between the Old Church -- the Church of huge gothic cathedrals, burning incense and incantations sung in Latin and the New Church -- youth groups, parish picnics and Christian rock. The Order, the latest offering from writer-director-producer Brian Helgeland, is a fresh new film about the lingering remnants of the Old.

The film follows Alex (Heath Ledger), a young priest of the Old ilk and a member of the Carolingians, a medieval order of exorcist priests. After his mentor, Father Dominic, dies mysteriously in Rome, Alex immediately flies to the scene to uncover the truth. Accompanying him are Mara (Shannyn Sossamon), a woman for whom he secretly, illicitly yearns, and Thomas (Mark Addy), a jovial Carolingian and longtime friend of Alex's.

The realm into which Alex plunges is not the Rome of tourist attractions, but one of shadowy rituals as immersed in physical darkness as in spiritual. Cinematographer Nicola Pecorini expertly casts the film in such murky tones, that ultimately we feel as if we are personally wandering through the cold, cavernous halls of an ageless Roman cathedral.

It is here that Alex and Thomas assume the roles of detectives investigating a murder, as they wield their crucifixes like .45's to ward off evil spirits that get in their way. And they do run into a few, the most significant of which is William Eden (Benno Furmann). I will not spoil anything by revealing the nature of Eden's powers, beyond my submission that he will be a fascinating figure for viewers to contemplate.

There is a lot that is compelling about Helgeland's third, and by far his best, directorial effort. Still, there are flaws in this one too. For instance, early on a radiant flash of light convinces us we have just witnessed something supernatural and Helgeland rightly lets our imaginations do the rest, but later we are subjected to seeing the same process repeated -- although this time juiced up with gaudy digital effects.

These reduce what was an abstraction of incomprehensible brilliance into a rather cheesy-looking wow 'em effect, an annoying and expensive tendency in movies these days.

Also, there is a weak side story that involves the attempts of an American cardinal, played by Robocop, to become the "dark Pope," but this subplot is abandoned for far too long in the middle of the story to sustain the audience's interest until it shows up again near the end.

Thankfully, Alex, Mara, Eden and Thomas dominate most of the film's spectacular third act, which is as unpredictable as it is tonally consistent, a rarity in mainstream films.

The Order is part horror, part romance, part mystery, part thriller and altogether a haunting, memorable effort.