Continuity mistake: When Harold's manuscript is wrapped up and tied with string, we see three closeups of the front with large black writing. The first closeup is when Harold holds it before he leaves, second when Mary holds it while on the train, and third when Roger Thornby holds it before opening it. The problem is there is no writing whatsoever on the front of the wrapping in all other shots. (00:24:00 - 00:38:25)
Continuity mistake: Harold takes a bottle of chloroform away from his young nephew and puts it in his pocket. The label says "Chloroform, 2% alcohol." Twice at dinner, Harold looks at the bottle and a close-up is shown. In the second close-up the "2% alcohol" is missing from the label.