And then the movie loses momentum. The next hour or so of the movie kind of drags, as it centers on the family of one of the victims. It has a lot of comic relief - it's originally Korean, and sometimes it's hard to tell if the tongue-in-cheek humor is intentional or just bad dubbing - but the humor can only sustain you for so long. Even the monster eventually gets boring, which is why most horror movies keep it hidden until the climax - this movie has no "payoff" scene. I kept hoping that they'd kill it, only to find a larger, weirder monster lurking in the shadows. Spoiler alert: Nope.
Basically, the whole movie feels backwards. It's as if you're watching one of those really slow, suspenseful horror movies, the kind filled with long scenes of exposition followed by quick flashes of monster killing someone, until the big-budget reveal scene right before they kill it. Except, you've decided to watch the ending first.
So rent this one, and rent it now. The opening is worth it. But if you start to get bored, and want to hit the fast-forward button, I promise not to tell anyone.