Wasting virtually no time on introductions, the movie plunges right in to Union's Shaun and her two kids going to the house of her estranged father, who we've seen die in the pre-credit sequence. Shaun is there to handle the sale of the house, a high-security, remote retreat that he acquired through unspecified ill-gotten gains.Unfortunately, a quartet of conveniently inept thieves have set their sights on the place, hoping to abscond with a mountain of cash hidden therein. Shaun thus finds herself trying to outwit them and save her children, in what becomes a protracted game of cat and mouse that eventually flips the script, turning the hunted into the hunter.The leader of the invaders, played by Billy Burke, seems more irritated than anything over having this wrench thrown into his grand scheme. Clearly, Shaun is capable of a lot more than the customary carpool drop-off, for reasons hinted at in glancing fashion during a fleeting call to her husband before all heck breaks loose.Of course, as a shared theatrical experience, some of the sillier moments (and there are several) actually serve a purpose, offering bits of comic relief — intended or otherwise — to offset the tension associated with skulking around in the shadows and flinging open doors. Operating on what amounts to a shoestring, director James McTeigue deserves some credit for milking a premise the encompasses few characters and even less real estate for not-quite 90 minutes.It helps that Union (who doubled as a producer) brings plenty of conviction to this thinly written exercise, which makes her heroics more plausible than they frankly have any right to be."Breaking In" was clearly designed as much a marketing proposition as a movie, a thriller whose twist on the formula is predicated in part on casting an African-American woman in the kind of role generally inhabited by guys like Liam Neeson — and as an added bonus, just in time for Mother's Day.While that hardly qualifies as a breakthrough, for those seeking a few mindless thrills, unlike the bandits, you've come to the right place."Breaking In" opens May 11 in the U.S. It's rated PG-13.