Line of sight

The line of sight is the “path” between an observer's eye and an object or person, which the observer looks at. Someone viewing the observer isn't always certain where the observer's gaze is focused.

Stories where the line of sight is uncertain

 * A Caribbean Mystery - When Major Palgrave is about to show Miss Marple the photo of a murderer he sees someone whom he recognises. Since the Major has a glass eye, Miss Marple can't be sure of the direction of his line of sight.
 * The Mirror Crack'd from Side to Side - Marina Gregg looks at someone/something when Heather Badcock spoke about their first meeting.