One of the scariest, most original scream-at-the-screen style horror movies I've seen in years, "Ghost Ship" is nonetheless ruined by such an insultingly insipid cliché of an ending that the last few minutes bring it crashing back down to the level of a stale slasher sequel.

But since detailing how it's ultimately sabotaged would spoil to the rest of the picture -- which remains stomach-knotting and wild shiver-inducing -- I'm going to pretend for now that I never saw the idiotic epilogue and focus on the crackerjack chills that come before.

The story unfolds as a mercenary marine salvage tugboat, acting on a tip from an Alaskan postal pilot, comes upon a mysteriously abandoned (and eerily radar-invisible) Italian luxury liner, adrift in a remote corner of the Bering Sea 40 years after it vanished without a trace. The tug's crew, lead by salty captain Murphy (Gabriel Byrne) and daredevil jack-of-all-trades Epps (Julianna Margulies), think they've hit the shipwreck jackpot -- until they slowly realize the dark, rusting, creaking, semi-submerged hulk is haunted from mast to keel and bow to stern.

Creeping along its dark corridors with flashlights, Epps is the first to catch a startling glimpse of a ghostly little girl in a frilly dress (the sweetly angelic yet hypnotically apprehensive Emily Browning) who, in a tantalizing twist on formula, is to become her tormented spirit guide through the terror that ensues.

Knowing she won't be believed if she tell her crewmates what she's seen, Epps keeps her spooked feelings to herself as the salvagers debate how to repair the ship enough to drag it back to port. Even after hearing the ethereal sound of a woman singing over their radios, finding a lit and lipsticked cigarette and stumbling onto a hold full of inexplicably fresh bodies, none of them are quite ready to leave the unearthly vessel because they've also found a fortune in gold bars onboard.

But by then it's too late. A hydrogen leak explosion sinks their tug and soon apparitions that send shudders surging through your bones are stalking the salvagers one by one.

Directed by Steven Beck -- who makes exponential improvements over "Thir13en Ghosts," his last, mind-numbing glossy gore-fest -- "Ghost Ship" lets trepidation build up methodically and allows for misleading moments of comic relief, as when a salvager played by Isaiah Washington finds himself in a dilapidated ballroom coming back to life around him. Wallpaper creeps back up the walls, the chandelier un-shatters and leaps from the floor to the ceiling, tables turn upright, dinner plates and wine glasses replenish with cuisine and suddenly he's surrounded by passengers while a sultry torch singer -- whose photo he'd seen on a decaying placard before entering the room -- seduces him.

"Francesca," he says in bewilderment (her name was on the placard), "I know all this isn't real, so I'm just gonna go with it, OK?"

Ooooh, big mistake.

In one of the movie's creepiest moments, the ghostly girl takes Epps' hand and reveals in a supernatural vision the ship's macabre history (a little of which we've seen in a bloody prologue deceptively filmed like a 1950s romance) and the hellish reason their souls are still on board. It's so invigorating to see a true horror movie (not a supernatural thriller like "The Sixth Sense") written with enough intelligence, by original screenwriter Mark Hanlon, to explain its horrors without leaving gaping holes in the plot.

Unfortunately this flashback is also the point at which the movie begins to hemorrhage innovation, acumen and imagination -- for which I largely blame a rewrite by John Pogue, who was responsible for this year's unwatchable "Rollerball" remake. These visions from the past are accompanied by a senselessly loud and incongruously modern hard-rock club mix on the soundtrack, signaling the formulaic, pop-horror direction the rest of "Ghost Ship" will take.

Until the film gets torpedoed by its hackneyed finale, there are only a few very nit-picky impediments to becoming thoroughly enveloped in its dynamically ominous atmosphere (which owes a lot to production designer Graham "Grace" Walker, "Pitch Black"). It's not only singularly unnerving; it has distinctive performances from a great cast as well.

So to properly enjoy "Ghost Ship" without having the experience marred by its downhill slide, here's what I suggest: When you see a modern cruise ship on the horizon, it's time to head for the exit. By that point you'll already know everything you need to know, without being exposed to sequel-baiting idiocy that follows.