The Courts of the Morning by John Buchan

Archie took a good quarter of an hour to disentangle himself from his Absalom-like posture, since, owing to the constriction of his garments, he could not get at his knife, and his hands were numb with cold. When at last he was free, he pitched forward stiffly into a huge tree-fern, which kept him from rolling down the slope. The actual forest was thin, but the undergrowth was dense and waterlogged, and the declivity so steep that every step must be watched. The fog was still there, but it was not thick, and a faint light filtered through it, so that it was possible to see the ground beneath and the trees above in a dim monotint.

His first business must be to find Geordie Hamilton. He shouted, but it was like speaking with the mouth muffled by folds of blanket. He argued that Hamilton must have descended not more than two hundred yards below him, and that the plane when he left it had been directly ascending the mountain face, so he tried to shape a straight course downhill. But the going was appalling. There were thickets of cactus to be circumvented, an occasional tall tree choked with creepers, and strips of sheer red earth. He stopped every few yards to shout for his companion, but no answer came; it seemed impossible to pierce that deathly stillness. Presently he realised that at this rate he would soon be lost. He halted and mopped his brow, for he was sweating under the burden of his heavy flying-clothes. And then he heard, apparently from the bowels of the earth, what seemed to be a groan.