A ray of light had shot out across the moat at a point some twenty yards in front of them. It came from the castle, and was rendered more vivid by the intense darkness elsewhere. The two diverged from the path now until they came opposite to the spot whence the light proceeded. It streamed from a window at some distance from the ground in an otherwise blank wall which connected two Gothic towers. There was nothing, of course, mysterious or even remarkable in the appearance of the light, which was, indeed, rather to be expected than the utter darkness in which all the back part of the castle had been shrouded, yet somehow both men felt that there was an element of mystery about it. For one thing, the room whence it came was situated at about the most distant point from that other lighted window they had seen from below, while all the intervening block of buildings seemed dark and silent as a ruin.

“I should like,” said Galabin, “to take the liberty of looking inside that room.”

“Impossible, so far as one can see,” Von Tressen replied. “There is nothing but sheer wall. Still, we might creep across and examine it.”

Keeping well outside the band of light which stretched slantwise across the moat, they descended into its hollow and crept up the other side. So much of it, that is, as they found practicable. For the angle made by the inner bank only rose about eight or ten feet from the bottom and then continued in sheer, straight stone wall. The two men were now directly underneath the window from which the light passed high over their heads; but, although they listened intently they could detect no sound from the room above them. To think of climbing the wall was absurd. At that part, at any rate, the stones were smoothly laid and faced, no hold for hands or feet was possible. After a thorough examination both men agreed that it was not feasible.

“If only some of yonder trees grew this side of the moat,” Von Tressen observed.

“Ah!” An idea occurred to his friend. “Suppose we climb one as it is and try what we can see. We shall at least get on a level with the window.”

Von Tressen nodded, and they stealthily recrossed the dip and regained the shelter of the wood.

“Let me go up and take an observation,” Von Tressen proposed. “I used to be a good climber.”

Selecting the foremost tree opposite the window, the Lieutenant with some little difficulty swarmed up the bare trunk. Galabin stood below eagerly watching his progress, which became easier as he got higher and the stem grew narrower. At length he calculated that Von Tressen must be on a level with the window, and drew back to measure the distance with his eye. As he did so, suddenly and silently the light vanished. He turned quickly, only to see nothing but a mass of black wall rising indistinct in the darkness. It was some minutes before he heard his companion descending; perhaps he had lingered in the hope that the light might re-appear, for assuredly nothing was to be seen in its absence.

“Just too late,” Von Tressen exclaimed regretfully, as he reached the ground. “It was provoking; but, never mind, we may have better luck another night.”