Ascending diagonally and in a westerly direction in the hope of crossing von Harben's trail, Tarzan moved constantly in the opposite direction from that taken by the man he sought. It was his intention, however, when he reached the summit, if he had in the meantime found no trace of von Harben, to turn directly eastward and search at a higher altitude in the opposite direction. As he proceeded, the slope became steeper and more rugged until at one point near the western end of the mountain mass he encountered an almost perpendicular barrier high up on the mountainside along the base of which he picked his precarious way among loose bowlders that had fallen from above. Underbrush and stunted trees extended at different points from the forest below quite up to the base of the vertical escarpment. So engrossed was the ape-man in the dangerous business of picking his way along the mountainside that he gave little heed to anything beyond the necessities of the trail and his constant search for the spoor of von Harben, and so he did not see the little group of black warriors that were gazing up at him from the shelter of a clump of trees far down the slope, nor did Nkima, usually as alert as his master, have eyes or ears for anything beyond the immediate exigencies of the trail. Nkima was unhappy. The wind blew and Nkima did not like the wind. All about him he smelled the spoor of Sheeta, the panther, while he considered the paucity and stunted nature of the few trees along the way that his master had chosen. From time to time he noted, with sinking heart, ledges just above them from which Sheeta might spring down upon them; and the way was a way of terror for little Nkima. Now they had come to a particularly precarious point upon the mountainside. A sheer cliff rose above them on their right and at their left the mountainside fell away so steeply that as Tarzan advanced his body was pressed closely against the granite face of the cliff as he sought a foothold upon the ledge of loose rubble. Just ahead of them the cliff shouldered out boldly against the distant skies. Perhaps beyond that clear-cut corner the going might be better. If it should develop that it was worse, Tarzan realized that he must turn back. At the turn where the footing was narrowest a stone gave beneath Tarzan's foot, throwing him off his balance for an instant and at that same instant Nkima, thinking that Tarzan was falling, shrieked and leaped from his shoulder, giving the ape-man's body just the impetus that was required to overbalance it entirely. The mountainside below was steep, though not perpendicular, and if Nkima had not pushed the ape-man outward he doubtless would have slid but a short distance before being able to stay his fall, but as it was he lunged headforemost down the embankment, rolling and tumbling for a short distance over the loose rock until his body was brought to a stop by one of the many stunted trees that clung tenaciously to the wind-swept slope.