“To go on with the thought—since Field’s hat was a tophat, and since nobody left the theatre dressed in a tophat who was not wearing evening clothes—this we watched for very closely—therefore the man who took away the missing hat _must_ have been garbed in full dress. You might say that a man planning such a crime in advance would have come to the theatre without a hat, and therefore would have none to dispose of. But if you will stop to think, you must see that this is highly improbable. He would have been quite conspicuous, especially while entering the theatre, if he went in minus a tophat. It was a possibility, of course, and we kept it in mind; but we reasoned that a man working out such a consummate crime as this would have shied from taking any unnecessary chance of being identified. Also, Ellery had satisfied his own mind that the murderer had no foreknowledge of the Field hat’s importance. This made still more improbable the possibility that the murderer arrived without a hat of his own. Having a hat of his own, he might have disposed of it, we thought, during the first intermission—which is to say, before the crime was committed. But Ellery’s deductions proving the murderer’s lack of foreknowledge made this impossible, since he would not have known at the first intermission of the _necessity_ of doing away with his own hat. At any rate, I think we were justified in assuming that our man had to leave his own hat in the theatre and that it must have been a tophat. Does it follow so far?” “It seems logical enough,” admitted Sampson, “though very complicated.” “You have no idea how complicated it was,” said the Inspector grimly, “since at the same time we had to bear in mind the other possibilities—such as the man walking out with Field’s hat being not the murderer but an accomplice. But let’s get on. “The next question we asked ourselves was this: what _happened_ to the tophat which the murderer left behind in the theatre? What did he do with it? Where did he leave it? ... I can tell you that was a puzzler. We had ransacked the place from top to bottom. True, we found several hats backstage which Mrs. Phillips, the wardrobe-mistress, identified as the personal property of various actors. But none of these was a personally owned tophat. Where then was the tophat which the murderer had left behind in the theatre? Ellery with his usual acumen struck right at the heart of the truth. He said to himself, ‘The murderer’s tophat must be here. We have not found any tophat whose presence is remarkable or out of the ordinary. Therefore the tophat we are seeking must be one whose presence is _not_ out of the ordinary.’ Fundamental? Almost ridiculously so. And yet I myself did not think of it.