Adapted from a novel by Dennis Lehane (whose work also inspired Mystic River and Gone Baby Gone), the fourth collaboration between Martin Scorsese and Leonardo DiCaprio stars the latter as US Marshal Edward Daniels, who in 1954 is dispatched with this new partner (Mark Ruffalo) to the Ashecliffe facility on the titular island, a prison/hospital for violent, mentally ill criminals run by Dr Cawley (Ben Kingsley) and Dr Naehring (Max von Sydow), where one of the patients has disappeared from her locked room. Her presumed escape seems to be impossible, the staff are remarkably unhelpful, and Daniels has a theory about something much darker and more sinister being conducted on the island… Naturally there’s an almighty twist, which will either keep you guessing or you’ll spot early on so you can brag about how you thought it was very predictable in order to make yourself look big and clever on online comment sections (because that works).

In fairness, the twist — or, at least, key elements of it — are fairly guessable if you’re playing that game. Equally, the film leaves enough doors of possibility open that if you set your heart on one answer (even the right one) then you’re perhaps being a bit blinkered and not indulging in the fun of being strung along by a well-built mystery. And as I always say, most twists are only “predictable” if you predicted the right thing. The mystery certainly kept me engrossed and guessing. I did suspect certain things that turned out to be correct, but there were enough other possibilities floating around that I wasn’t twiddling my thumbs waiting for the reveal.

Besides, the film has other delights beyond being an elaborate guessing game. One of the things Lehane set out to do in his novel was write “a gothic”, and Scorsese and co have taken that ball and run with it. It’s overflowing with a fantastic atmosphere: unsettling, creepy, chilling, horror-movie scary when needed (some sequences are properly hair-raising); truly gothic-feeling. Every aspect of filmmaking — the direction, the photography, the editing, the sets and locations, the music — work in harmony to create a coherent mood.

To single out two, it’s gorgeously shot by Robert Richardson. There are a couple of dream sequences that are a show-off for that kind of thing, but it’s true more widely, the storm-bedevilled island presenting a rewardingly overcast palette. There are instances of what one might call dodgy green screen… but, combined with the continuity-troubled editing, I sense it may’ve been a conscious choice to enhance the disquieting sensation (the editing is certainly deliberate — that some commenters seem to believe Scorsese and Thelma Schoonmaker could make so many basic errors is bizarre).

The second is the music, put together by Robbie Robertson. Scorsese and Robertson decided against a traditional score, instead choosing to compile fragments of other works (many of them anachronistic) and chop them up in different ways. It’s probably to Robertson’s credit that it doesn’t feel like a jukebox soundtrack; indeed, I assumed it did have a fully composed score, and really rather liked parts of it.

And then, after Scorsese and co have done their best to shred your nerves, in the final half-hour the pathos is immense. Quite without realising it had brought me to that point, I had a tear in my eye. This is in part thanks to some great performances, though you do need to reach the twist to fully appreciate them. Everyone reveals more levels once you know it, and indeed it’s clear a great amount of effort went into ensuring re-watchability — that if you view it again knowing the answers, you can spot things; not clues, per se, but elements in the performance, the design, the staging, that tie in to the reveal.

DiCaprio has the showiest performance, though he never goes too far with it — it’s resolutely plausible at all times. Ruffalo may give the best turn of them all, in retrospect — if you watch it a second time (or, for a quick fix, check out the clip-laden making-of documentaries where they discuss the acting), you can really see what he’s doing. Kingsley, too, who without changing his performance is both threatening and kindly.

Incidentally, reviews criticise the brevity of the documentaries on the Blu-ray, but with over half-an-hour of content they could be considerably worse, and they’re quite focused — I learnt a lot from them. No, you’re not getting a scene-by-scene breakdown like you would in an audio commentary, and there’s minimal detail on the usual moviemaking details, but there’s a solid overview of the film’s themes and how they were translated to the screen.

I think the more you let Shutter Island percolate after it’s over, the better it becomes. Solving the mystery and guessing at the twists occupies so much of your time on a first viewing that you almost miss the details in the characters and the world, but they build up nonetheless. There’s layers and depth here, and a plausibly realistic depiction (even according to an expert) of something that’s incredibly hard to depict in fiction. You can view Shutter Island as just an atmospheric gothic mystery chiller, and as that it’s a quality piece of work, but it’s the extra depth that mark it out as, actually, a great movie.

The UK network TV premiere of Shutter Island is on Channel 4 tonight at 9pm.

Shutter Island placed 16th on my list of The 20 Best Films I Saw For the First Time in 2015, which can be read in full here.