Far away from the site of a gruesome murder, a teenager named Jill Johnson arrives at a luxurious home for a baby-sitting job. With the children fast asleep, she settles in for what she expects to be an ordinary evening. Soon, the ringing of a phone and the frightening words of a sadistic caller turn Jill’s routine experience into a night of terror.

Based on a famous stage play and set in the year 1912, an upper crust English family dinner is interrupted by a police inspector who brings news that a girl known to everyone present has died in suspicious circumstances. It seems that any or all of them could have had a hand in her death. But who is the mysterious Inspector and what can he want of them?