I Saw the Devil, a proudly in-poor-taste thriller about predators playing with their food, opens on a serial killer who's a methodical madman—not unlike, you might say, the filmmakers, who plot their first act with the propulsive precision of expert pulp novelists; think Jim Thompson, or even Cormac McCarthy. The movie's first forty minutes or so—in which special agent and widower Soo-hyeon (Lee Byung-hun) pursues his fiancée's killer while the butcher, Kyung-Chul (Oldboy's Choi Min-sik), stalks fresh prey—is refreshingly efficient: emotional, but never indulgent; psychological, but only broadly, like an issue of Detective Comics. Its focus never strays from The Hunts, its pared-down, parallel procedurals—psychokiller and vigilante, not so much mouse and cat as cat and, um, bigger cat.
When the two converge, the opening act comes to a breathless close and I Saw the Devil devolves into gimmick: bereaved defeats bereaver but, instead of killing him, lets him go and tracks him from a distance. It's a sick game for both character and director: like the audience, Soo-hyeon follows this despicable cretin's adventures, but he also has the superpower of intervention, doing what the viewer never can—pop into the frame every time Kyung-Chul begins to hurt someone else and stop him. It lets director Kim (The Good, the Bad and the Weird) and his screenwriter Park Hoon-jung have it both ways: to revel in both villainy and its resulting heroism, to take glee in both the bad guy's lechery—indulging in the same misogyny that marred Na Hong-jin's The Chaser—and the good guy's sadistic retribution.
The filmmakers ditch efficiency for sensationalism. Mean-spiritedly long at 141 minutes, I Saw the Devil blends extraordinary gore with comedy both black and babyish: Kim is not above having his villain dig through his own diarrhea, or slip on scattered jacks like a Home Alone burglar. The director pretends, though, in regularly timed scenes of guilt-stricken anguish, that his message is still serious: that vengeance comes at a great cost. It's hard to take it seriously, though, when the director clearly relishes the good guy's righteous bloodbaths. At one point, the dead fiancée's sister tries to talk Soo-hyeon out of his obsession with retaliation. "This is pointless," she says. Agreed.