Disturbia is a savagely efficient eyewitness-to-murder thriller, a Rear Window for the YouTube generation.

It's an occasionally comic high school romance wrapped in grief and violence. Those shifts in tone may give you whiplash, but the third act's by-the-book payoff does what it's designed to do -- pay off.

This film from the writer of Red Eye and the director of Two for the Money takes Alfred Hitchcock's great Rear Window conceit, that we're all voyeurs when we go to the movies, and ratchets it up for a more plugged-in age. What is privacy to kids who reveal their deepest secrets, or dishonest versions of them, to MySpace, kids growing up in a world of security cameras and Internet security breaches?

Photo Gallery: Disturbia
A father-son fishing trip ends in tragedy, and Kale (Shia LaBeouf) has to carry around grief and guilt for the rest of his life, or at least for the rest of high school. Cut to a year later, and he manages to punch a teacher out in the last days of a semester. He earns house arrest -- an electronic ankle bracelet -- for the summer.

Kale goes through a sugar-buzz/video game/isolation-induced stir craziness. Then, hot hot Ashley (Sarah Roemer of The Grudge 2) moves in next door, and Kale watches her. A lot. Is she teasing him? She seems to be watching him, too.

Wouldn't you know it, that's when the a missing person makes the news. Kale sees coincidences from the case that connect to a mysterious neighbor. He lets himself be distracted from Job One -- pursuing Ashley. Kale, his pal Ronnie (Aaron Yoo, a scene-stealer) and eventually Ashley work themselves into a tizzy over the guy who may be a serial killer, living right next door.

Smart casting move: David Morse is the mysterious Turner. He can be spooky and dangerous, or sad and misunderstood.

A blunder: The script doesn't let him play those shades. We believe the kids, that he's one bad hombre, from the get-go.

The movie plays around with the electronic bracelet idea, foreshadowing how Kale might make an asset out of his "spatially limited" existence. Routine ticking clock scenes put the kids in jeopardy. Cell phones and all manner of surveillance and home video gear give Disturbia a Blair Witch Project feel. Experiencing violence -- or a taste of it -- through a camcorder boosts the fear factor.

LaBeouf, of The Greatest Game Ever Played and Holes, captures the caffeine-jag awkwardness of his character's age and makes for a believably paranoid gearhead. His reasons for questioning Turner betray a teenager's understanding of privacy.

"Why does he want his privacy? What's he hiding?"

Where the movie stumbles is in its lack of a poker face. We know director D.J. Caruso's hand before he plays it -- too many "tells," too many obvious bits of foreshadowing.

But the chills are genuine. And there's something very rewarding about sitting through a new version of a movie any film buff knows by heart. The years may change the technology of how we spy on our neighbors, but not our desire to do it.