Why wouldn’t you just go to Canada for the night?

"The Purge" presents a utopian America in 2022. Crime is virtually nonexistent. Unemployment is at 1 percent. And it’s all because something called the New Founding Fathers — a concept that’s neither explored nor explained — created The Purge, a 12-hour period once a year in which all laws are suspended.

No one turns to rape. Nobody dedicates that night to knocking over banks. You’d think someone, somewhere would be gleefully bootlegging movies, ripping the tags off mattresses or smoking a joint the size of the Hindenburg on Capitol Hill.

But no. The Purge is basically a dusk-till-dawn murderthon, almost exclusively at the expense of the poor and downtrodden who can’t afford to defend themselves. The not-so-subtle side effect is the elimination of many of those who are seen as being a drain on the economy.

You can almost hear Karl Rove slapping himself in the head for not having thought of it first.

James Sandin (Ethan Hawke) adores The Purge. He’d make sweet, sweet love to it if he could. A decade ago, he was struggling to pay the rent. Now, he’s living in a newly expanded mansion thanks to all the money he’s made selling home security systems to the rest of his ritzy, gated community.

At its darkly funny best, "The Purge" presents those dozen hours as a sort of twisted national holiday. Friends and neighbors greet each other with "Safe night!" Talk-radio callers sound off about their Purge plans. Sandin’s next-door neighbor blithely sharpens a machete in his front yard. Even the night’s unofficial mantra - "Release the Beast!" - sounds more like the slogan of an energy drink than a government-sanctioned slaughterpalooza.

But as the wealthy - at least the ones who aren’t attending Purge parties - barricade themselves behind expensive steel shutters, it’s hard to shake the notion that it would be safer, easier and a heck of a lot cheaper to just leave for those 12 hours. Drive to Canada or Mexico. Take a cruise. Hover above the mayhem in a hot-air balloon. Whatever it takes to survive.

Sandin, though, just hunkers down with his family: wife Mary ("Game of Thrones’ " Lena Headey), sullen teen daughter Zoey (Adelaide Kane) and macabre son Charlie ("Parenthood’s" Max Burkholder), who’s obsessed with his grotesque, burnt baby doll-topped robotic camera that’s mostly just there to provide some stalker-style footage.

Shortly after the house is sealed off, Charlie hears a stranger (Edwin Hodge) crying for help and briefly interrupts the lockdown to offer him refuge.

Before long, the Sandins are under siege from a gaggle of heavily armed, upper-crust weirdos seeking an outlet for their Aryan rage amid talk of cleansing their souls.

They’re an odd lot in their sweaters, ties and crested blazers. And their grotesque, Joker-smile masks only add to the Stepford-y creepiness.

They don’t want to hurt their rich, WASP-y brethren. Really, they don’t. But they will if the Sandins don’t turn over the "dirty, homeless pig" they’re sheltering.

Sure, he’s wearing an Army jacket and dog tags. Odds are, he’s served his country far more than they ever will. But he’s down on his luck - and black, for crying out loud - so he’s got to go.

What follows is not so much a horror movie as an uglier spin on "Straw Dogs," "The Strangers" or even "Assault on Precinct 13," the 2005 remake of which also starred Hawke and was scripted by "The Purge" writer-director James DeMonaco.

"The Purge" wants to provoke more thoughts than it ultimately does, as the Sandins argue about the morality of saving themselves by sending a stranger to his death. Although at this particular screening, certain scenes brought out the Roman Colosseum spectator in many audience members.

After the introduction of a killer premise - literally and figuratively - "The Purge" mostly consists of a lot of creeping around in the dark and some fairly routine action. But it does so in a lean, efficient 85 minutes.

Thanks to its low budget and easily adaptable formula, "The Purge," much like The Purge, could become an annual event.

A sequel is already in the works.

Maybe then viewers could learn a little more about these New Founding Fathers.

And why anyone with even a modicum of means doesn’t simply make a run for the border.

Christopher Lawrence is the movie reviewer for the Las Vegas Review-Journal. Contact him at clawrence@reviewjournal.com.