So they toiled along for upwards of an hour. Young Marco ahead had not caught sight of the horsemen; there was no sign of the enemy in the rear. It was the old man’s hope that there would be time, if danger threatened, to rush the cart into some hollow or some gap between the rocks. Such a threat was more likely to arise from the scouting party than from the larger force behind, and the boy, as instructed by his grandfather, kept sufficiently in advance to give timely warning. The track was continuously up hill, broad at some points, at others so narrow that the cart was only just able to pass between the rocky borders, sometimes as low as kerbstones, sometimes rising to a height of many feet. The frequent windings prevented the travellers from getting a direct view for any considerable distance ahead. Every now and then they had glimpses of the watch-tower which Burton had previously noticed, and which they were gradually approaching. At such times he scanned it through his glasses, half expecting to find that some of the scouting party had ascended it to survey the surrounding country. But no human figures yet showed above the summit. At length, however, on rounding a corner, the travellers were startled by a sudden flash from the tower. They halted, Burton levelled his glasses, and declared that he saw two heads and pairs of shoulders projecting above the top. Other flashes followed, at intervals long or short. "They are heliographing to the main body behind us," he said to Enderby, repeating the information in French to the Serb. "Can they see us?" asked Enderby. "They might perhaps if they looked, but they are gazing far beyond us, of course. We had better back a little, though." They had, in fact, halted before the oxen had come completely into view from the tower, and by backing a few feet they were wholly concealed. The three men held an anxious consultation. The tower was probably two miles ahead. To go on would involve discovery by the enemy. On the other hand, parties of Bulgarians might already be marching up the track behind them. It seemed that they were trapped. "We had better wait a little," Burton concluded, "and see whether they leave the tower and go forward. In that case we might venture to proceed." The signalling continued for some few minutes, then ceased. The men disappeared from the summit of the tower. Burton was on the point of suggesting that they should move on when he caught sight of a small figure flitting rapidly from rock to rock down the track towards them. "It is the boy," he said, after a look through his glasses. In a few minutes young Marco arrived, excited and breathless. "Three horsemen are coming down the hill," he reported. "Tchk!" muttered the old man, repeating the news. "How far away, child?" "A mile or more. They are riding slowly; the track is steep."