Episode #1.1 - S1-E1
Continuity mistake: When he is asked "The culprit is a woman, isn't it?", the doctor is suddenly holding the pen between both hands instead of just with the right hand. (00:29:55)
Episode #1.1 - S1-E1
Factual error: The series is set in 1933, as the initial captions show. Yet the locomotive pulling the Orient Express is a JNR Class C58: the C58 series was built starting from 1938 (C58 239 used here is from 1940).