Park Chan-wook's Oldboy won the Grand Prix at Cannes in 2004, selected by a jury chaired by Quentin Tarantino. The affinities between the two filmmakers are unmistakable. Both work with what used to be called pulp material, dressing it in expertly crafted packages derived in equal parts from low and high culture. Like Tarantino, Park has an impressive grasp of film grammar, especially exploitation techniques. Why an undeniably talented director would devote so much passion and energy to material like this is the most pressing puzzling aspect of Oldboy.

The title refers to a high school that businessman Oh Dae-su (Choi Min-sik) attended as a youth. Now a husband and father, Oh is arrested one rainy night while drunk. Without explanation, he is spirited away to what looks like a shabby motel room. Oh is imprisoned there for the next 15 years, during which time he is framed for his wife's murder.

Rescued from his suicide attempts, Oh devotes himself to relentless physical training. When it arrives, his release is as inexplicable as his imprisonment. Although free, Oh still seems under surveillance. Mysterious clues lead him to a Japanese restaurant, where he befriends Mido (Gang Hye-jung), a pretty sushi chef.

With Mido's help, Oh locates the office building where he was imprisoned. An audiotape there suggests that Oh is being tormented by an unknown enemy. Oh eventually learns that his nemesis is Lee Woo-jin (Yoo Ji-tae), once a high-school classmate. Lee gives Oh five days to solve the reason for their enmity, or he will be killed.

The first half of Oldboy proceeds with an inexorable drive that is grimly compelling. Director Park fleshes out the story with precise, harrowing details, like the dried-out trails of blood staining the rug in Oh Dae-su's motel cell. But the mystery surrounding Oh gives way to a repugnant tale of revenge.

Oldboy has several visually searing moments. Gossip about the film has centered around an encounter at the sushi restaurant between Oh and an octopus that's clearly alive (four were required to film the scene). More remarkable is a tracking shot in which Oh is assaulted by scores of thugs as he makes his way down a corridor-a set-up that reportedly took three days to shoot.

But no matter how accomplished Park is as a filmmaker, there is no escaping Oldboy's gratuitously vile plot elements. The director takes an almost clinical approach to the film's lurid physical and psychological violence, in the process reducing a ferocious performance by Choi Min-sik to a sick joke. Park has tested limits before in his films, but he always had at least the pretext of a higher moral purpose. Here, he seems content to just toy with viewers' sensibilities for no other reason than a few cheap shocks.