We all pretend we were that teenager. Down on her luck, no cash from the parents, desperate to make ends meet, and then she gets the call. A wealthy family with a big house who just need her to watch the kids overnight. They'll sleep through all of it.
This lucky girl tucks the kids in at 7, and because it's a fiction, they don't make a peep. She's wandering the mansion and pocketing their candy bars when her cell rings. In older versions of the story it's the house phone, but who has one of those anymore?
"Hello?" she asks.
The response is heavy breathing, like the caller has been sprinting. It goes on for a few seconds before he hangs up.
She thinks that's weird, and Caller ID says it's an unknown number. Maybe a friend from school butt-dialed her. She's walking into the next room when her cell rings again.
Heavier breathing this time, labored like it's coming through a cloth. She's about to threaten the call-troll when he hangs up again.
She goes to the foyer, looking out the windows, because if you've even heard of Horror movies, you look out the God-damned windows when this happens to you. There's no one there. She's convincing herself it was a dumb prank when her cell rings again. This time the shock is so great she almost throws it at the wall.
"Who the hell is this?"
There's more muffled breathing, and what sounds eerily close to a child's giggle. Then a muffled voice asks, "Have you checked the children?"