Mildmay nodded, and seizing their rifles, the pair, with infinite caution, parted the veiling reeds just sufficiently to afford them a glimpse in the direction from which the sound had proceeded. And there, within half a dozen yards of them, their eager gaze fell upon a troop of some thirty--horses? Well, they were, in appearance, like the horses one sees represented in Greek sculpture; rather short in the body, round in the barrel, with slim, elegantly shaped, but apparently very strong legs, and they carried their heads high upon thick, muscular, arching necks. They stood about fourteen hands high, and were of a beautiful deep cream colour, with short black manes, black switched tails similar to that of the gemsbok, and their legs were black from the knee downward. But their most remarkable characteristic was that the stallions were provided with a single, straight, black, sharply pointed horn, some three feet in length, projecting from the very centre of the forehead, two or three inches above the level of the eyes. They were descending the slope that led down to the water, and were advancing at a walk, their paces being singularly graceful and easy. Their leader, an exceedingly fine and handsome animal, was a yard or two in advance of the rest, and, with arching neck and head carried somewhat low, he came on, peering alertly right and left, evidently on the watch for possible enemies. "We must get a pair--two pairs if we can," murmured von Schalckenberg in a low tone, rendered hoarse by excitement and anxiety. "You take the leader and another stallion, I will look out for the mares. Aim for just behind the shoulder. Are you ready?" "Yes," breathed Mildmay. "Then _fire_!" whispered the professor. And, as the rifle-hammers softly clicked, the thud of the bullets was heard, and the leader and a handsome mare dropped, shot through the heart. The troop halted instantly, snorting nervously and glancing quickly to right and left, clearly puzzled at this sudden and unaccountable fall of two of their number. Quick as thought the hidden sportsmen each selected a fresh victim, and ere one could count ten another pair of the beautiful creatures were down. This was enough; the unicorns now realised that some mysterious deadly influence was at work among them, and, throwing up their heads, they swerved short round and dashed off up the slope again, over the ridge of which they vanished the next moment, uttering shrill neighs of alarm.