All at once the yak uttered a cry and burst from his control, leaping past him and darting on in a panic till it vanished down the narrow slope toward the north. Stones kicked by its flying hooves fell over the brink of the quarry and lost themselves in the dark without any sound of striking bottom; but Carter ignored the perils of that scanty path as he raced breathlessly after the flying steed. Soon the left-hand cliffs resumed their course, making the way once more a narrow lane; and still the traveller leaped on after the yak whose great wide prints told of its desperate flight.