It's 1954 and Detective Teddy Daniels (Leonardo DiCaprio) and his partner Chuck Aule (Mark Ruffalo) are sent to investigate the disappearance of a patient from an island prison housing the criminally insane.
As Daniels begins to spot potential leads through the hospital employees, he is introduced to the mysterious Dr. Cawley (Ben Kingsley) who refuses to reveal staff records in order to aid with the investigation.
Daniels continues to be haunted by his own flashbacks to a moment in the Second World War where he is infiltrating a Prisoner of War camp and punishing the guards and is constantly guided by his dead wife during the investigation.
He begins to wonder whether they are all interlinked and whether there is something far more sinister going on.
Deep down every Martin Scorsese film is practically the same. The are all dark and desperately confusing but somehow leave the audience feeling as though they have watched a masterpiece by the time the credits role. Don't worry, Shutter Island is no different. In fact, in the 15 minutes prior to those closing credits Shutter Island provides so many twists it makes it seem as if the previous two hours was just padding so that this self-satisfaction would be all the more sweet.
As mentioned, the first couple of hours are horrifically confusing; in fact, the way to sum up Shutter Island could be as a "whodunnit" - albeit without knowing what "who" did. Perhaps "whodunwot" would be a far more accurate summation. DiCaprio's acting reflects this confusion as a man who is battling with his inner demons to solve a crime that isn't necessarily even a crime.
As you call tell, it is truly difficult to put down in writing the content of the story without giving too much away. A second viewing is essential - this review was written after my second look at the film, and, from experience, the whole story is completely turned on its head the second time around.
According to various other reviews and synopsis' that have compared the film to its counterpart novel by Dennis Lehane, DiCaprio's final words are about the only thing that aren't true to the book. Scorsese shows that, with a singular line and some of his famous theatrical touches, he can turn a perfect novel into a perfect film. This is how film adaptations should be done.