Alarms go off in the minds of nine-year old Austrian twins Lukas and Elias when their mother returns home from the hospital after an accident. Bandages from reconstructive surgery make mom’s face look like a mummified skull, but underneath her behavior is so different that the boys convince themselves that she’s an impostor. Less a horror movie than a psychological thriller about how awful children are, the boys set mom up for an increasingly gory series of challenges in order to to figure out the truth.