They were in the grim, dusty house at last. Jack was conscious only of the intense darkness and musty smell of the place. Carefully piloted by Rigby, he reached the second floor landing at length, and there Rigby grasped his arm significantly. There was no sound at first save the scratching of mice behind the panel or the flutter of some ragged blind swayed in the piercing draught. Then suddenly it seemed to Jack that a solemn footfall sounded in a room close by, a door opened with a pop like a pistol crack, and a long slit of light, dazzling in its brilliancy, fell like a lance upon the dusty floor. Somebody laughed somewhere, a laugh that sounded so near and yet so far away; then the door opened wider, and a partial view of the interior of the room could be seen.

Utterly taken by surprise, moved and horrified to the depths of his soul, Jack could have cried out, but for the hand clapped upon his mouth like a steel trap.

"Not a sound," Rigby whispered sternly. "For heaven's sake, restrain yourself, and look, look!"

[CHAPTER XI.]

THE SHADOW ON THE WALL.

Jack needed no second bidding; he was only too anxious and eager to follow the direction of Rigby's outstretched finger. He was by no means lacking in the nerve and pluck which generally go to a young man of fine physique and clean habit. But there was something about the whole of this affair, a creeping suggestion of diabolical crime, such as one only encounters in the wildest realms of fiction.

And yet it seemed to Jack that his reading of the daily press recalled things just as vile in every-day life. With teeth clenched firmly, with a stern resolution to do nothing very likely to precipitate what might have been a terrible catastrophe, Jack looked into the room before him. As the door was half open and the two friends were hidden in the blackish shadow, it was possible to watch without the slightest chance of being seen.

For an empty house, dusty and gloomy and deserted as it was, the room in front of our two adventurers presented a striking contrast to the rest of the place. There was no window, or at least, where the window ought to have been, something in the way of an iron shutter stood, and over this a great wealth of silken hangings was artistically arranged. As to the rest of the apartment, the furniture was directly in keeping with the abode of a millionaire. Jack did not fail to notice the rich Persian carpet, the luxurious chairs and settees of the First Empire period, the fine pictures on the walls. The walls, too, had been recently decorated, so that there was not a single jarring note to mar the harmonious whole. There were flowers, too, grouped in the corners of the room and piled cunningly around the electrolier standing on the centre table.

"Now, that is a strange thing," Jack whispered. "So far as I could see, so far as I can see now, there is no sign whatever of the electric lighting in any other part of the house. Do you suppose that these people have taken this house in the ordinary way, or is it possible that----"

"Not a bit of it," Rigby replied. "They're not the sort of people to do anything as foolish as that. Nor would there be any occasion to go to the expense. Depend upon it, they know all about the character of the owner of this property, and that it is not in the least likely to let unless put thoroughly in order."