No matter how great the filmmaker behind the camera, a movie is only as good as its screenplay.

Martin Scorsese may be the best director working today, but even he can’t steer “Shutter Island” away from its fundamental story problems. Moody atmosphere, convincing period art direction and an island stocked of A-list actors just can’t save the film from a predictable, tedious plot.

Based on a novel by Dennis Lehane (“Mystic River”), “Shutter Island” takes place in 1954 at a hospital for the criminally insane located on a remote, Northeastern island. A disturbed murderer has disappeared from her cell, so two U.S. Marshals (Leonardo DiCaprio and Mark Ruffalo) are called in to investigate. A couple immediate warning signs for the officers: The guards won’t let them bring in their firearms, and the hospital doctors (Ben Kingsley and Max von Sydow) exude a level of vague creepiness typically reserved for villains on “Lost” island.

Marshal Teddy Daniels (DiCaprio) yields some emotional baggage of his own. In addition to a splitting migraine, Teddy keeps having visions of his dead wife (she burned in a fire) and a pile of bodies he witnessed while liberating a concentration camp during World War II. Teddy soon begins to believe that the doctors and guards on Shutter Island are involved in some kooky government conspiracy.

It’s also raining really, really hard.

DiCaprio is convincing as he tries to decipher the truth from paranoia and his dreams from reality. Sadly, the actor is stuck in an emotional loop for much of the movie. Teddy’s flashbacks and dreams often revert back to the same disturbing imagery over and over again, leaving little opportunity for the film to generate any tension from them.

Scorsese clearly wants this movie to be unsettling, and he piles on a bombastic score that tries to hit viewers with a general feeling of apprehension. Unfortunately, very little of “Shutter Island” generates thrills. There’s one sprawling, exciting sequence that finds Teddy tiptoeing through the darkened halls of the island’s most dangerous criminal ward, and a confrontation with prisoner Jackie Earle Haley will stick with audiences much longer than any of the so-called “twists” that follow.

Scorsese is a masterful director, so he isn’t really capable of making a bad film. He makes good on the technical side of things, richening “Shutter Island” with some eye-catching camera moves and 50s atmosphere. There isn’t a weak link in the performances either, and Kingsley, von Sydow, Ruffalo, Patricia Clarkson and Michelle Williams (as Teddy’s dead wife) make the most out of the thinly-developed plotting that involves their characters.

If only the story wasn’t so predictable. With a 2 hour, 20 minute running length, “Shutter Island” takes too long to get to a punchline some might be able to guess within the first 10 minutes. Even if the film had a stunning twist, Scorsese would still have been stuck with material below his pay grade.

Grade: B-