In the beginning of the story, Mrs Stevenson is home alone and is trying to get a hold of her husband.
She repeatedly tries to get the operator to call her husband but her husband isn't picking up the phone. She is getting worried.
The operator connects her to a line and then she overhears two men plotting a murder. They discuss details about the murder and give the time for the murder.
Mrs Stevenson is trying to tell the operator and the police there is going to be a murder but she has no evidence to prove it's going to happen. Nobody believes her.
While she's talking to the operator about there's someone coming for her, she hears someone downstairs. She's home alone so nobody is supposed to be in her home. She asks the operator to please call the police.
Her murderer comes into the room and she is on hold with the operator. The police Chief is connected to the phone. The murderer picks up the phone and tells the police nothing is wrong there and he must have the wrong number.