Young Marco, to his disappointment, was left to guard the cart and to keep a lookout. The old man hastened with Burton to the spot where Captain Enderby lay beside the wreck of the aeroplane. As they went, Burton caught sight of a square tower on a hill-top far away to the south. "What is that?" he asked. "An old watch-tower," replied the Serb. "There are many such on high points in different parts of the country." Burton paused a moment to scan the solitary tower through his field glasses, then resumed his course. On reaching the fallen man, the old Serb at once set about placing the injured limb in splints formed out of the wreckage, preparatory to carrying him back to the cart. He was still thus engaged when Marco came running up the gully. "Grandfather," he said, breathlessly, "a party of horsemen are coming up the side track." "How many are they, boy?" "Ten or twelve. They are far away." "I must go back," said the old man. "You will still be safe here." "I will go with you," said Burton. "My glasses may be useful." They followed the boy, who ran ahead, regained the cart, and went beyond it to the point where the two tracks met. The sky had now cleared, and the white-clad country glistened in the sunlight. Keeping under cover, Burton peered through his glasses along the winding track. At first he saw nobody, but presently a horseman came into sight round a bend, followed closely by two more riding abreast. After a short interval, another couple appeared, the first file of a party of ten, riding two by two. They were still too far distant for Burton to distinguish anything more than that they were in military uniform. He told the old man what he had seen. "Beyond doubt they are Bulgars," the Serb growled, drawing his fingers through his beard, which the sunlight had thawed. He stood silent for a little, his eyes fixed in thought, his hands working nervously. "They will overtake us," he said at length. "We must move the cart from the track. Come, monsieur." They hurried back to the cart. At a word from the old man the woman dismounted, and going to the heads of the oxen, led them off the track over the rough ground of the hill-face, while the three others set their shoulders to the wheels. By their united efforts the unwieldy vehicle was hauled round the shoulder of the hill towards the gully, to a spot two or three hundred yards from the aeroplane, where it was out of sight from either of the tracks. Leaving it there in charge of Marco and his mother, the two men returned, obliterating the traces of the wheels in the snow, and finally posting themselves behind a rocky ridge near the junction of the tracks, where they could see the approaching horsemen when they should pass, without being seen themselves. III