At least it didn't go the Lynch route.

Rating: 6/10 (3 March 2016)

While investigating the disappearance of a murderess from a hospital for the criminally insane, US Marshal Teddy Daniels (Leonardo DiCaprio) comes to suspect the staff of using the prisoners for medical experiments.
Halfway through Martin Scorsese's Shutter Island and two possibilities crossed my mind: the first and most disconcerting was that the film would be a totally incomprehensible piece of self-indulgent surrealistic nonsense; my other concern was that, after two and half hours, it might finish with a supposedly clever but actually rather trite explanation for the events that had occurred—like the main character being one of the institute's patients, for example. But this is Scorsese, I reasoned, he surely wouldn't pull a Lynch or a Nolan on me.
Think again, Brett
After much confusion, Scorsese does indeed wrap up matters by revealing that Leonardo DiCaprio's character is a few sandwiches short of a picnic, having lost his marbles after shooting his wife for drowning their three children. It's far from the most unpredictable of twists, but—and this is a BIG 'but'—Scorsese's masterful direction (there's creepy atmosphere in abundance) and a strong central performance from DiCaprio ensure that the film is still a reasonably entertaining ride despite the frustratingly foreseeable denouement.