To Jill Johnson, it was the perfect babysitting job. The parents were away. The fridge was stocked. The children were tucked into bed. But then the phone rings and an ominous voice asks, "Have you checked the children?" Locked in with the lights out and the curtains drawn, a panicky Jill phones the police, who trace the calls - only to inform her they're coming from inside the house. And as the frightened teenager goes upstairs to check on the children, Jill's quiet night of babysitting is about to turn into a nerve-shattering nightmare of suspense, horror and dread.