Oldboy

Imagine what you'd do, when you wake from a bad dream, to find you're held by four square walls, for as long as someone deems. No idea why you're trapped, what you've done, why you're kidnapped, just a ceaseless line of dumplings going down your gyoza hatch. Now some fifteen years have passed, every question has been asked, and you're suddenly set free, can start your own avenging spree. Before you do you need to feed, by eating something that's in need, so an octopus is ordered, and head first you cross the borders. But things aren't what they might seem, tied and tethered and undreamed, as the puppet master hovers, manipulates what you'll discover.

Some films you cannot watch too often and this is one of the greatest pieces of cinematic brilliance ever created.