"We must give it up," said Bob wearily. "Unless Nurla has got him he's either at the bottom of the river, or else washed down miles by this time."

"I don't care about caving in altogether," said Lawrence. "It would be some satisfaction--a mournful one--to recover his body and give him decent burial."

"Poor old man! He wouldn't care a bit about that. What's more to the point is to hunt down the blackguards who killed him. That's what I propose to do as soon as our men come up. Some of them are sure to know the country, and with them on horseback and ourselves in the aeroplane, I'd take long odds that we find Nurla in time."

As they talked, they kept their eyes on the river, more from the habit engendered during the previous few hours than with any strong hope of their search being rewarded. Presently Lawrence, following with his eyes the foaming ripples as they swirled down-stream, caught sight of something that caused him to spring to his feet with a sudden ejaculation and lift the field-glass to his eyes.

"What is it?" asked Bob, rising also.

Lawrence handed him the glass. Far away he saw, rounding a bend in the track, a party of horsemen marching slowly in single file towards them. Their costume proclaimed them as Kalmucks, and though they were too far distant for their features to be distinguished, the shape of the foremost seemed to be that of the dwarf, Black Jack.

The watchers suddenly remembered the encampment over which they had flown earlier in the day. The same thought flashed simultaneously through their minds: the stealthy proceedings of Nurla in the mine and his subsequent disappearance had not, then, been prompted by an indefinite hope of gain; they had been deliberately planned, either in the knowledge of the proximity of a body of his fellow countrymen, or even in concert with them. There could hardly be a doubt that, as once before, an attempt was to be made to dispossess Mr. Appleton of his mine.

The boys stood watching only for a moment or two; then they dropped down, feeling instinctively that it behoved them to keep out of sight. But brief though their gaze had been, it was long enough to assure them that the approaching party was a numerous one. They counted a dozen men; others were coming round the bend, and they were strung out along the track. Every man had a fire-arm of some sort, a carbine, or a rifle, or a long musket like the Afghan jazail.

For the moment even the fate of their uncle was obliterated from the boys' minds by this astonishing discovery. They realized that their own lives and the safety of the mine were in danger. Hitherto their anxious thoughts had been fixed on one object alone; now they saw themselves faced with a much more complicated problem.

"We must get back," said Bob, insensibly lowering his tone of voice. "We can do nothing at present for Uncle. We must at least return to the aeroplane and wait to see what happens. I'm pretty sure I'm right: those fellows are being led by the dwarf--and Nurla too, I suspect--to the mine. Luckily we've plenty of time to fly back in the aeroplane and give warning."