"Quite easily. After I left you this afternoon I went back to the agent and succeeded in obtaining possession of the keys of the empty house in Portsmouth Square. My excuse was that I wanted to go into detail and to take measurements and the like. I need not remind you that Bates' house is next door to the empty one. In fact, there is no question that both houses belong to the same person. You will remember, also, the mysterious way in which that furniture vanished from the scene of your adventure." "I remember," Gurdon said grimly. "But all the same I don't quite see what you are driving at." "The thing is quite plain. That furniture did not vanish through the prosaic medium of a van, nor was it carted through the front door from one house to the other. The two houses communicated in some way, and it will be our business to find the door. As I have the keys and every legitimate excuse for being on the premises, we can proceed to make our investigations without the slightest secrecy, and without the least fear of awkward questions being asked. Now do you follow me?" "I follow you fast enough. I suppose your game is to try and get into the next house by means of the door?" "You have hit it exactly," Venner said. "That is precisely what I mean to do. We shall find it necessary to discover the identity of Mr. Bates' tenant." "When are we going to make the experiment?" Gurdon asked. "We are going to make it now," Venner replied. "We will have a cab as far as the Empire Hotel, so that I can get the keys. After that, the thing will be quite easy. Come along, and thank me for an exciting evening's adventure. I shall be greatly surprised if it is not even more exciting than the last occasion." They were in the empty house at last. The windows were closed and shuttered, so that it was possible to use matches in the various rooms without attracting attention from the outside. But search how they would, for upwards of two hours, they could find no trace whatever of a means of communication between the two houses. They tapped the walls and sounded the skirtings, but without success. Venner paced the floor of the drawing-room moodily, racking his brains to discover a way out of the difficulty. "It must be here somewhere," he muttered. "I am sure all that furniture was moved backwards and forwards through some door, and a wide one at that." "Then it must be on the ground floor," Gurdon remarked. "When you come to think of it, some of that furniture was so heavy and massive that it would not go through an ordinary doorway, neither could it have been brought upstairs without the assistance of two or three men of great strength. We shall have to look for it in the hall; if we don't find it there, we shall have to give it up as a bad job and try some other plan." "I am inclined to think you are right," Venner said. "Let us go down and see. At any rate, there is one consolation. If we fail to-night we can come again to-morrow."