Continuity mistake: In the red drawing room, Freddie Nesbitt can be seen behind his wife, Mabel, putting his coffee cup on a bureau. They cut away to a wider shot, and he is holding the cup again.
Continuity mistake: When Henry Denton storms out of the room after the coffee is spilled in his lap, Lady Trentham's newspaper is open. As she starts to laugh, the camera angle changes and her paper is now closed and she reopens it. (01:49:55)
Continuity mistake: While Mrs Wilson questions Inspector Thompson about when the staff may leave and he lends his matches to Arthur, the door behind the Inspector is open. However, in the next shot Mrs Croft opens the door to enter the room. (01:46:39)
Continuity mistake: When Lady Trentham knocks on the window in the car, Mary looks at her over her right shoulder but when the camera angle changes she is looking over her left shoulder.
Continuity mistake: While investigating the murder of Sir William, the constable examines the coffee cup that Sir William shattered when the housekeeper attempted to give it to him. The floor beneath the shards of the cup is clean, there is no residue from the spilled coffee.
Continuity mistake: When Emily Watson is pinning the hem of Maggie Smith's dress just before she goes down for dinner, the neclace that Maggie Smith is wearing is quite long, the pendant almost can't be seen by the dress and then the next shot the pendant is half way up her neck, and has become a lot shorter.