It's nearly impossible to predict cinematic sleeper hits. We just looked at some of this summer's arthouse candidates in light of the "Kings of Summer" release last Friday. But in the end, there's no perfect rubric. And the off-the-wall guesswork is particularly apparent after the weekend's top earner was the home invasion thriller "The Purge."

Things get scary in "The Purge," last weekend's surprise hit. (Daniel McFadden)

The premise? For 12 hours each year, all crimes are legal. So one family (led by Ethan Hawke and Lena Headey) has to fend for itself when a group of masked killers comes knocking. The movie took the top spot at the box office and raked in $36.4 million. For comparison, "The Internship," which stars Owen Wilson and Vince Vaughn, came in fourth with $18.1 million (and a much larger budget).

In other box office news, "Fast & Furious 6" and "Stark Trek: Into Darkness" have both crossed the $200 million threshold. "The Hangover Part III," meanwhile, has now brought in more than $100 million domestically, raising the question of whether this will actually be the end of the trilogy, as promised.

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