The Mysterious Affair at Styles - S3-E1
Continuity mistake: The guests of Styles Court manage to get inside the room of Mrs. Inglethorp and talk to her before the second fatal crisis happens. In the first wide shot you can see Hastings peek at Lawrence and then look towards the fireplace, which is an action he'll do in the close-up that follows - Lawrence does not seem to look in the direction Hastings is checking out, at all, but that is actually a nice touch considering the resolution. Moreover, in the second close-up of Hastings looking at him (the one that follows the view of the fireplace), Mary is directly in front of Hastings, you can see her insignia and arm. But instantly she is shown at the cut, creeping along the wall behind Lawrence. (00:29:00)