Starring Leonardo DiCaprio and Mark Ruffalo. Rated 14A. Opens Friday, February 19

There are so many well-kept secrets lovingly salted throughout Martin Scorsese’s Shutter Island that it would be a shame to reveal more than a wisp of the plot.

Set in 1954, and based on Dennis Lehane’s novel, the movie opens with U.S. marshal Teddy Daniels (Leonardo DiCaprio) getting to know his new partner (Mark Ruffalo). The pair are headed toward an island hospital for the criminally insane, a place of such unspeakable sorrow that it’s virtually quarantined in the middle of Boston Harbour. Their mission? To investigate the mysterious disappearance of a dangerous inmate.

We soon discover that Teddy is tormented by his troubled past. Haunted by the experience of liberating Dachau, he endures terrifying nightmares. He’s also trying to cope with the tragic death of his wife Dolores (Michelle Williams). When Dolores begins to appear as a tenderly beautiful apparition, providing her husband with cryptic warnings about his current case, Teddy can’t help but revel in the longing for everything he’s lost.

When an approaching hurricane traps an increasingly suspicious Teddy on the island, he interrogates a number of enigmatic characters. He focuses on the hospital’s chief psychiatrist (Ben Kingsley), a man whose courtly demeanor can’t disguise the fact that he’s hiding something of great significance. In the hands of a lesser director, all of this would be reduced to the cheap melodrama of a standard horror film. But Scorsese creates a complex world best described as gothic-noir, a shadowy place where dreams and reality merge so seamlessly that we’re completely seduced.

While it’s a pleasure to watch a uniformly inspired cast lure us into a state of mounting uncertainty, Shutter Island delivers much more than thrills. It’s wise, vulnerable, and achingly sad, tempting us into the darkest corners with just enough light to make everything seem undeniably human.