So well had the preparations been made that an hour amply sufficed for the loading up, and at the end of that time the two troops of camels were standing, each with its own drivers, a short distance apart, and nothing remained but for those who rode to mount and the order to be given for the start. It was just then that a tall, dark object, the one for which the doctor had been anxiously looking, loomed up from the Baggara camp and stalked silently up to where the Baggara chiefs son lay waiting upon his rug. As it reached his side, attended by two men, the great camel was stopped, and its load was more plainly to be seen, shaping itself into a couple of rudely made, elongated panniers, out of one of which, while it was held, a man leapt lightly out, the other being occupied by one of the weakest of the wounded. The doctor and Frank then superintended the lifting in of the chiefs son, who bore the movement without a sigh, and the great camel, after the rug had been laid across like a form of housing, was led back to its fellows, some twenty yards away. Then from out of the darkness an order rang out, and the waiting camels were mounted, after which there was the snorting of horses, and half a dozen graceful creatures trotted by to take the lead as advance guard, the troop waiting till they were a little distance ahead. At last the shadowy looking line of camels, horses, and men were awaiting the order to start, for some reason unaccountably delayed, when suddenly the Sheikh laid his hand upon Frank's arm. "Hark!" he whispered excitedly. "Listen! Do you not hear?" Frank shook his head. "It is quite plain," continued the Sheikh. "Horses--the trampling of many men. Keep close together, Excellencies, while I warn my people." "Warn them of what?" said the doctor calmly. "Danger, Excellency. These may be friends coming, but it may mean an attack or the coming of strangers. If it is either of the latter I shall try to lead you all into safety. So at a word follow me at once straight away into the desert. We may be able to escape." The Sheikh's camel glided silently away into the darkness, and the party sat straining their sense of hearing to the utmost, making out plainly enough now the dull sound of trampling hoofs, the jingling of trappings, and every now and then an angry snort or squeal as some ill-tempered beast resented the too near approach of one of its own kind. Then all at once, as the sounds came nearer, there was heard plainly enough the muttering, whining cry of a camel, followed by more and more proofs then that the coming party was one of greater strength than it had seemed to be at first. Just then the Sheikh came back out of the darkness, to halt his camel close up by the professor's. "It is not English cavalry, Excellencies," he said, "but a native force. I think it must be the Baggara chief and his men returned."