 The second puzzling fact was the armchair pulled out from its normal place in the study and that can only have been to have hidden something from sight at the moment that the room was broken into.As the Dictaphone is missing, it can only be that item which was there and, by use of a time-lock, the voice heard behind the door was not that of the living Sir Roger but a previously-made recording – the man was already dead.The murderer can only be someone who had a receptacle to carry away the machine and who had the study to himself for a moment after the discovery of the body – in other word's, Dr. Sheppard himself.