"If any difficulties are placed in the way of these gentlemen's investigations, I shall make it my duty to bring the facts before the Home Secretary," announced the professor; speaking up to the ceiling with the voice of a brazen trumpet. Carrados raised a deprecating hand. "May I make a suggestion?" he remarked. "Now; I am blind. If, therefore----?" "Very well," acquiesced the manager. "But I must request the others to withdraw." For five minutes Carrados followed the list of safe-renters as the manager read them to him. Sometimes he stopped the catalogue to reflect a moment; now and then he brushed a finger-tip over a written signature and compared it with another. Occasionally a password interested him. But when the list came to an end he continued to look into space without any sign of enlightenment. "So much is perfectly clear and yet so much is incredible," he mused. "You insist that you alone have been in charge for the last six months?" "I have not been away a day this year." "Meals?" "I have my lunch sent in." "And this room could not be entered without your knowledge while you were about the place?" "It is impossible. The door is fitted with a powerful spring and a feather-touch self-acting lock. It cannot be left unlocked unless you deliberately prop it open." "And, with your knowledge, no one has had an opportunity of having access to this book?" "No," was the reply. Carrados stood up and began to put on his gloves. "Then I must decline to pursue my investigation any further," he said icily. "Why?" stammered the manager. "Because I have positive reason for believing that you are deceiving me." "Pray sit down, Mr Carrados. It is quite true that when you put the last question to me a circumstance rushed into my mind which--so far as the strict letter was concerned--might seem to demand 'Yes' instead of 'No.' But not in the spirit of your inquiry. It would be absurd to attach any importance to the incident I refer to." "That would be for me to judge." "You shall do so, Mr Carrados. I live at Windermere Mansions with my sister. A few months ago she got to know a married couple who had recently come to the opposite flat. The husband was a middle-aged, scholarly man who spent most of his time in the British Museum. His wife's tastes were different; she was much younger, brighter, gayer; a mere girl in fact, one of the most charming and unaffected I have ever met. My sister Amelia does not readily----" "Stop!" exclaimed Carrados. "A studious middle-aged man and a charming young wife! Be as brief as possible. If there is any chance it may turn on a matter of minutes at the ports. She came here, of course?"