Hugh, somehow, fixed the fact of his comrade's presence on his mind.

He even mentally figured just how long it was likely to take the other to reach the spot where he himself had left the road; or, perhaps, that circumstance might loom up large in his calculations.
Then he arrived at the brink of what seemed to e a precipice.

The presence of this told Hugh plainly the nature of the task that awaited him.

Someone had undoubtedly fallen over the brink, and was, even then, hanging on desperately to some jutting rock or bush that represented the only hope of safety from a serious fall.

He threw himself down and thrust his head out over the edge.