It's been 14 years since Shutter Island was released, and tbh we're still getting over the film's ending.
In fact, it has to be up there with one of the best movie twists of all time.
But did you know there was actually a prop that Leonardo DiCaprio used during filming that pointed to the jaw-dropping finale all along?
If it wasn't already clear, there are spoilers ahead.
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The psychological thriller was adapted from author Dennis Lehane’s bestselling book, and followed DiCaprio as he took on the role of US Marshal Teddy Daniels, who was sent to an institution for those deemed criminally insane to investigate a missing patient.
Viewers witness flashbacks throughout the movie, letting us know that Teddy has a complex history, but it's not clear exactly what happened to him.
In fact, it's not until the end of the film that the US Marshal learns he's actually a patient at the institution himself; one who was sent there after murdering his wife after she drowns their children.
It turns out that the whole 'missing patient' narrative was something Teddy came up with to help him deal with the trauma.
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The staff decide to go along with it to see if it will help him accept reality, but it doesn't work and he's given a lobotomy instead.
It's a corker of an ending - which is actually very different in the book.
After finding out who Teddy really is, and re-watching the film, viewers have noticed one tiny clue which points to the truth all along.
A video uploaded by movie buff @imeugeneclark explains that a prop used in the film reveals that Teddy was a patient all along.
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"Did you know that in Shutter Island a small detail reveals Teddy's true identity early on?" they explain.
"Of course, a big plot twist of the movie is finding out that Teddy Daniels isn't in fact a US Marshal but actually Andrew Laeddis, a patient at the mental sanatorium he is investigating.
"This twist is actually given away as every time that Teddy goes to smoke a cigarette, someone else lights it for him.
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"This is because patients on Shutter Island are not permitted to carry lighters around with them."
Other fans pointed out more clues, including the fact that Teddy's formal clothes are too big for him (because they aren't his) and that his 'partner' Chuck struggles to take off his holster before entering the facility, because he isn't used to it.
"It's one of the earliest clues that his partner isn't who he says he is, since someone with his supposed background shouldn't be struggling with such a simple action," they wrote on Reddit.
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Others claimed the reason why Teddy doesn't light cigarettes is because of his past.
"Its actually because he’s terrified of fire because of his past, same reason he’s scared of the water throughout the movie," they wrote.
Meanwhile others are still convinced that Teddy was a US Marshal and he was simply tricked.
"To this day, I still believe that they tricked him and that he’s in fact a federal marshal," they commented.
What do you think?
Featured Image Credit: Paramount PicturesTopics: TV and Film, Leonardo DiCaprio