I'm working on a novel that is essentially a search and pursuit by a 65 year old man for a murderer he thought he saw when he was 13. He's not sure if he saw it or not because he seems to have repressed the real memory of it, but the scene has been haunting him in his dreams ever since it happened. Or when he thinks it might have happened. Somebody here posted in a previous post that there is an Agatha Christie story with a similar theme. I didn't note it down at the time. Do you know what it is please?
