Like the book on which it's based, Martin Scorsese's "Shutter Island" leaves you sandbagged and gasping, although not in exactly the same way. The movie oozes gore and dementia — it has the dripping atmosphere of a gothic horror film. And the wild plot twist in Dennis Lehane's lurid 2003 novel, from which the picture has been adapted with iron fidelity, may be even more shocking in its transposition to the visual realm. Like the book, though, the movie is unleavened by humor or any other narrative respite. This isn't a problem in print, where we can pull back from the material; but it makes the picture a grueling experience, and the fact that it's too long makes it even more arduous.

The story is set in 1954. As it opens, we see U.S. Marshal Teddy Daniels (Leonardo DiCaprio, in his fourth Scorsese outing) and his new partner, Chuck Aule (Mark Ruffalo), arriving by ferry at the remote and craggy Shutter Island, site of the Ashecliffe Hospital for the Criminally Insane. The marshals have come to help find an escaped murderer, Rachel Solando, who has mysteriously disappeared from her locked cell. But Teddy also has a personal agenda: He's heard that a man named Laeddis — a deranged pyromaniac who set a fire two years earlier that killed Teddy's wife — is also an inmate here. What he wants to do to Laeddis if he finds him is unclear: Teddy tells Chuck that he already did enough killing in the war, which still haunts him with gruesome memories of Dachau, the notorious concentration camp he helped liberate.

Ashecliffe is a very strange place. Its director, the imperious Dr. Cawley (Ben Kingsley), is obstinately unhelpful; and no one, it seems, has ever heard of anybody named Laeddis. As for what goes on in that abandoned lighthouse just off the island's shore ... don't worry about that. There's also the matter of the hospital's population. Cawley says there are only 66 patients; but then Teddy finds a note hidden in the vanished Rachel's cell that asks, "Who is 67?" When Teddy becomes bothersome about all of this, the chief psychiatrist, a sinister German named Naehring (Max von Sydow), fixes him with a chilly smirk: "I'm very impressed by your defense mechanisms," he says.

Teddy becomes plagued by hallucinations, much in the way the movie is plagued by flashbacks. We're continually being pulled away from the linear narrative and transported somewhere else — back to Dachau, to watch a dying Nazi twitching in a pool of his own blood, or into a nightmare room where leaves are falling and the walls are going up in flames. These scenes are integral parts of the story, not just artsy ornaments, and Scorsese renders them with an infernal lyricism. But there are so many of them, and they're sometimes so rapturously lyrical, that after a while they begin to seem a little silly — especially when Teddy's dead wife, Dolores (Michelle Williams), turns up for an eerie chat, as she does frequently. (On the other hand, a long scene involving Dolores and Teddy by the side of a lake is a masterful exercise in controlled, concentrated horror.)

What with all the squealing rats and queasy lobotomy lore and staring dead children packed into the story, we understand Teddy's feelings when he decides it's time to go. But then a storm comes gusting up, knocking out the phone lines to the mainland and killing the electrical power — which among other things keeps the patients' cell doors locked. Will Teddy ever get out of this place? Dr. Cawley suddenly seems to think not.

DiCaprio, an actor whose adult work has often been at war with his unaging boyish face, is more convincing than usual here (despite a variable Boston accent) as a troubled man veering back and forth between hostility and helpless disorientation. Kingsley and his little goatee are sleekly diabolical, Jackie Earle Haley and Elias Koteas are the scariest of the crazies on hand, and Patricia Clarkson gives a brief, beautifully modulated performance as a woman whose revelations set the story sliding off in a disturbing new direction.

In a movie that for the most part is pretty grim, Scorsese's occasional Hitchcock flourishes — the rear-projection backgrounds in some of the outdoor scenes, the lighthouse looming up like the windmill in "Foreign Correspondent" — provide welcome amusement. It's puzzling, though, that the director agreed to let screenwriter Laeta Kalogridis overstep Lehane's perfect ending in order to conclude the film with a trite, tacked-on question that goes annoyingly unanswered. "Shutter Island" isn't a perfect piece of work (although it may seem better in years to come), but there are sequences in it that soar and burn. It's not a pleasant picture, but it's a powerful one.

"Shutter Island" is a Paramount Pictures release. Paramount and MTV are both subsidiaries of Viacom.

Don't miss Kurt Loder's review of "The Ghost Writer," also new in theaters this week.

Check out everything we've got on "Shutter Island."

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