midnight
But may he not have been there before the room was locked . Nay , he must have been there before ! Let us look into the matter of these traces and see if they do not point to my conclusion . `` After the publication of the article in the ` Matin ' and my conversation with the examining magistrate on the journey from Paris to Epinaysur-Orge , I was certain that `` The Yellow Room '' had been hermetically sealed , so to speak , and that consequently the murderer had escaped before Mademoiselle Stangerson had gone into her chamber at midnight . `` At the time I was much puzzled . Mademoiselle Stangerson could not have been her own murderer , since the evidences pointed to some other person . The assassin , then , had come before .