He was close to it now, so close indeed that, with a cautious movement of his arm, he could touch the sheet. A single prick with a sharp point of his knife gave him all the information that he needed. It was a sheet of paper surely enough. A moment later Rigby was standing by Jack's side once more.

"Paper," he whispered. "Really, this adventure is likely to prove prosaic after all. Don't you think we are rather making a mountain out of a molehill? We know that Anstruther is a great rascal, but at the same time he is an exceedingly clever man, and, as you know, inclined to be secretive. Now, isn't it just possible that our friend has hit upon some new process of photo-lithography, and that we are witnessing an experiment to demonstrate the value of the new idea."

"I don't think so," Jack replied. "Indeed, since you have been away, I have made something in the way of a discovery also. Mark well the picture thrown upon the screen yonder. You know what it represents, of course?"

"Well, naturally. I have seen the diabolical face of Nostalgo on too many posters not to be absolutely familiar with his ugly mug. Depend upon it, those fellows are printing the famous poster in some way known to themselves. Maybe we shall see that self-same sheet on some hoarding to-morrow."

"But that is not what I meant at all," Jack proceeded to explain. "If you are as familiar with the poster as you say you are, you will notice a considerable difference in this one. In the first place, the face is a little more in profile, and surely you must notice the difference in the hands."

"Right you are," Rigby replied. "In the present instance the hands are half-extended, as if in the act of clutching something. Strange that I had not noticed that before. What do you make it out to be?"

"Hush!" Jack whispered. "I think our ingenious friend behind the lantern will explain that for himself."

The leading operator in the room gave a short curt sign and the brilliant lights flashed up once more. The slide was also drawn from the lantern, but the sinister features of the dark, repulsive face upon the screen did not vanish as might have been expected. On the contrary, the grim face frowned down as if it had been brushwork from the pencil of some imaginative artist. One of the workmen approached the sheet and dragged it to the floor. Then the three men in the room bent over the poster and examined it critically.

"It seems to me that the hand is a little out of drawing," the leader of the trio remarked critically. "Give me the paints--the white paint, I mean."

The speaker took a brush heavily charged with some white pigment and proceeded to touch up the hand. He cut this portion from the sheet and placed it in the slide of the lantern. Then another large sheet of paper was erected in front of the window, and the lights turned out again. Almost immediately there appeared upon the disc the shadow of a huge, bony hand uplifting a dagger in a menacing attitude. A grunt of approval came from the man behind the lantern, and once more the lights were turned up.