“What do you do when the last visitor has gone?” “Having locked the outside door, Beale, here, thoroughly examines every room to make certain that no one remains concealed. He next locks the communicating doors and comes down into the hall. It was then his custom to hand me the keys. I gave them into poor Conway’s keeping when he came on duty at half-past six, and every hour he went through the Museum, relocking all the doors behind him.” “I understand that there is a tell-tale watch in each room?” “Yes. That in the Greek Room registers 4 A.M., so that it was about then that he met his death. He had evidently opened the door communicating with the next room--that containing the broken glass case; but he did not touch the detector and the door was found open this morning.” “Someone must have lain concealed there and sprung upon him as he entered.” “Impossible! There is no other means of entrance or exit. The three windows are iron-barred and they have not been tampered with. Moreover, the watch shows that he was there at three o’clock, and nothing larger than a mouse could find shelter in the place; there is nowhere a man could hide.” “Then the murderer followed him into the Greek Room.” “Might I venture to point out that, had he done so, he would have been there this morning when Beale arrived? The door of the Greek Room was locked and the keys were found inside upon the floor!” “The thief might have had a duplicate set.” “Quite impossible; but, granting the impossible, how did he get in, since the hall door was bolted and barred?” “We must assume that he succeeded in concealing himself before the Museum was closed.” “The assumption is not permissible, in view of the fact that Beale and I both examined the rooms last night prior to handing the keys to Conway. However, again granting the impossible, how did he get out?” The Scotland Yard man removed his hat and mopped his forehead with his handkerchief. “I must say, sir, it is a very strange thing,” he said; “but how about the iron door here?” “It leads to my own apartments. I, alone, hold a key. It was locked.” A brief examination served to show that exit from any of the barred windows was impossible. “Well, sir,” said the detective, “if the man had keys he could have come down into the hall and the lower room.” “Step down and look,” was Coram’s invitation. The windows of the room on the ground floor were also heavily protected, and it was easy to see that none of them had been opened. “Upon my word,” exclaimed the inspector, “it’s uncanny! He couldn’t have gone out by the hall door, because you say it was bolted and barred on the inside.” “It was,” replied Coram. “One moment, sir,” interrupted the plain-clothes man. “If that was so, how did you get in this morning?”