 High School student Jill Johnson agrees to baby sit while the Dr. and Mrs. enjoy a night on the town. After she tucks the children snuggly into bed, upstairs, telephone calls from a stranger begin to disrupt what she had planned as a quiet evening of study. At first, the unidentified caller says nothing which leads Jill to believe that an acquaintance is playing a joke. After several similar calls, she becomes unnerved and calls the police when the silent stranger still offers no clue to his identity. The phone calls continue... Finally, an eery voice on the other end of the line asks ominously "Have you checked the children, lately?" It appears that the stranger can see her and is aware of her movements. She closes all the curtains and turns out the lights believing that the darkness is her only hiding place. By this time, the police are tracing the origin of the calls. Jill is told she must stall for time, the next time he calls, so that the trace can be completed. More calls... "Why haven t you checked the children?" the caller asks. Jill, by now frightened nearly out of her wits, screams into the receiver "Leave me alone!" and slams the phone down onto it s cradle. Again, the phone rings, but this time it s the police who have successfully traced the call. "Jill," the detective says, "we ve traced the calls... They re coming from inside the house!"