Gleefully demonizing both the British “chav” working class and the horror genre’s usual target audience of mid-teen males, Eden Lake pits a well-to-do, soon-to-be-married couple (Kelly Reilly and Michael Fassbender) against a gang of obnoxious, bicycle-riding 14-year-olds. It’s the epitomical rule of these films: Never, ever get confrontational with disagreeable people. We know that if you’re out with your girl by a quiet lake and your peace is disturbed by a group of hormonally charged young jerks, you’ll be tempted to assert yourself, but seriously: Don’t. Just leave. Of course, then there’d be no movie. Writer-director James Watkins, who previously co-wrote the UK suspense flick My Little Eye, expertly plays on the viewer’s fears and prejudices—who among us hasn’t secretly wanted to smack the shit out of some wannabe-macho prepubescent bully? But you’ll likely feel queasy afterward, upon realizing the movie has you rooting for these lower-income kids to die at the hands of the disempowered yuppies. As a thriller, Eden Lake absolutely works, but feel-good entertainment it isn’t. Don’t bring a date.