When Drummond returns home after returning Phyllis' bag he turns on the car headlights to read the note that was left in his hat. He never turns them off before going inside, yet they were off when he goes out a few minutes later when Col Nielsen leaves.
Near the beginning, Drummond sees a dead body in the moor and sees it sink. At the end, Drummond leaves without telling about the corpse or tell anyone where the body is located. (But Col. Nielson does mention the "murdered chauffeur" well before the end.)