Shooting in sleek 35mm, Franz and Fiala have dreamt up a home-invasion scenario where the aggressors lived there all along, like the children in Ray Bradbury’s “The Veldt,” who lock their parents to their playroom to be devoured by lions. It was her or them, and in a freaky flip on things, it’s the kids who make the preemptive strike. Come to think of it, they were always hovering, doing that weird thing that only twins can where they speak in riddle and seem to read each other’s thoughts.