I pretended an assurance I was far from feeling. The cliff above the end of the arch looked sheer as a house wall and as smooth.

“They’re coming back again,” said Aryenis with a sigh of disappointment. “I don’t know any other way if we cannot climb that.”

I was more than disappointed. The possibility or otherwise of reaching the caves was probably life or death to us all. But we hadn’t told Aryenis that. Gloomily and silently we watched them make their way down.

However, on their arrival in camp, their report was a shade better than I had hoped, though none too good. They considered that with a little work the first part could be made easily practicable even for men with heavy loads, and the second part up to the foot of the arch was quite a gentle slope.

The arch itself was more difficult. It rose nearly three hundred feet according to Wrexham’s estimate, tapering upward and inward in a gentle curve, till at the centre it was not more than twelve or fourteen feet wide. However, with ropes the loads could be got up on to it.

But to get up the rock face to the caves was quite a different matter. If we could get people from above to let down ropes, it would be all right, though unpleasant. But Aryenis had said no one ever came there. So absolutely our only hope was for one of us to succeed in climbing up with the rope, and fix it to something in the cave by which to help the rest up.

“There’s a sloping seam in the rock stretching up to the cave mouth as far as we can see,” said Wrexham, drinking the tea Aryenis had poured out for him. “It doesn’t look to me as if it gave foothold to anything bigger than a lizard, but Alec, who’s done a lot of rock-climbing, thinks it might just be possible for a clever climber given a miraculous amount of luck. Anyway, it’s our only chance, and we’ve got to take it or give up and go back; and that, as you know, is at least even chances of pegging out while trying to get across the desert. The camels are pretty done now.”

He pulled out his pipe and lit it.

“Well, what are we going to do, then?” I asked, looking across to where Forsyth was talking to Aryenis.

“To-morrow we’ll all go up, leaving Firoz and Sadiq here with the camels. We’ll take every bit of rope we can scratch together, as well as the two one hundred fifty foot lengths of Alpine rope. Alec is going to make a shot at getting up the seam by himself. He says it’s no good two men going, because the rock is so sheer that if one slipped the other would be pulled off, too, and it’s no good chucking away two lives. I wanted to go, but he insisted, and as he’s done more climbing than I, although I’ve done a lot of crag-work at home in Durham, I caved in.