Then Tom noticed that the defile seemed to end in the air, as if it had arrived at the brink of a cliff. Creeping cautiously through the bush above the narrow path, they came to the top of the rise and looked over. It was not a cliff, as Tom had supposed; but a somewhat steep and rocky slope, dotted here and there with patches of coarse scrub. Down this slope two figures were moving: Haroun the Arab led, Reinecke was only a few paces behind him. When they came to the foot of the slope they halted, and talked somewhat excitedly together. Haroun pointed forward and downward; Reinecke stooped, looked over the edge of the slope, shook his head and apparently flew into a rage. Thereupon the Arab went alone over the brink, descended slowly, and passed out of the watchers’ sight. Reinecke sat down in a fissure, in the attitude of waiting. Tom had observed these movements at first with nothing more than a certain impersonal curiosity; but a suspicion of their meaning began to dawn when Haroun disappeared. The air was misty; from the spot where he crouched nothing was visible beyond the margin of the slope except the grey sky. But Reinecke, where he sat, evidently saw something more. Every now and again he bent over, following the progress of the Arab, and also, as it appeared, taking much interest in the scene below. "We are above the nullah," thought Tom. "That fellow Haroun must have discovered a way out and in. Our position is to be turned. My word!" Some twenty minutes passed. Haroun’s head reappeared at the edge of the slope. He spoke to Reinecke volubly, using his hands in free gestures, as though demonstrating a point. The German appeared to be convinced. He got up, stepped over the edge with the aid of the Arab’s hand, and followed the man slowly out of sight. CHAPTER XV--THE BACK DOOR "Run back and see if the askaris are still there," said Tom to Mwesa. The lad darted away through the bush that clothed the top of the bank of the defile. Returning in a few minutes, he reported that the enemy had not stirred from their position. "Then we will go on. Keep close to me." They made their way carefully down the slope. At the bottom they peeped over. A narrow cleft zigzagged down the face of a steep cliff, for the most part bare rock, but with trees and bushes growing here and there where soil gave them roothold. This vegetation and the windings of the cleft hid Reinecke and the Arab from sight; but several hundred feet below they could just discern, through the mist, the still surface of an expanse of water. Mwesa’s eyes opened wide with surprise. "Don’t speak," whispered Tom. "Yes; I think it is our lake."