Movies are often made by their endings, and if a filmmakers gets it wrong, it can catastrophically tank a film's reception.
After all, those final moments before the credits roll are going to linger in the viewer's brain as they leave the cinema, and if they stink, then the film as a whole is affected.
But get it right, and a great movie can become a sure-fire classic, leaving audiences on an elated, mesmerised high.
Some movies, however, dare to take a wholly different tack, simply aiming to bewilder and baffle as much as possible, and giving viewers a heap to digest as they head home.
It's fair to say that the entirety of Christopher Nolan's ingenious thriller is a bit of a head-scratcher, revolving around an amnesiac man, Leonard Shelby (Guy Pearce), attempting to track down his wife's rapist-murderer while battling against his inability to create new memories.
In an attempt to replicate Leonard's fractured mental state, the majority of the film's scenes unfold in reverse order, leading to the climactic mind-melter of a reveal that Shelby himself accidentally killed his wife by administering an insulin overdose to her due to his amnesia.
Throughout the film Leonard tells the story of Sammy Jankis (Stephen Toblowsky), a man who did very much the same thing to his wife, but of course, Sammy doesn't really exist, and the story is merely an attempt to assuage his own guilt over killing his wife.
The story concludes (and begins, chronologically speaking) with Leonard murdering Teddy (Joe Pantoliano), the man he believes to be the attacker. However, as we travel backwards, it's revealed that Teddy is in fact an uncover cop and helped Leonard kill the attacker a year prior.
Teddy has since been exploiting Leonard's amnesia to set up other unsavoury figures to be killed, prompting Leonard to leave himself a Polaroid falsely incriminating Teddy as the killer and eventually leading to his death.
Long story short: Leonard intentionally deceives himself into believing that Teddy was one of the attackers, creating his own revenge narrative to paper over the fact that he himself was unintentionally responsible for his wife's death. Grim.