The Fog Princes by Florence Warden

Rees Pennant was physically brave, but the sight of those staring eyes meeting his in the bowels of the earth gave him a shock which, in the state of excitement into which his recent adventures had thrown him, for the moment caused his mind to lose its balance. He thought the man was alive, and, reeling, began to murmur some hoarse words of explanation of his own intrusion; but they came forth in indistinct, guttural sounds through the tube which covered his mouth. His hand shook so much that the dying light in his lantern went suddenly out, leaving him in utter darkness. Losing his head altogether, he uttered a wild cry, and would have burst himself loose both from tube and rope if a strong pull at the latter had not suddenly called him to remembrance of Sep faithfully waiting for him in the vaulted chamber above.

The fact was that Rees, in his efforts to get as far as the length of the tube would allow, had given the three pulls which he had arranged between them as the signal for Sep to help him to return. In spite of himself, therefore, he felt that he was drawn backwards. He had been pulled two or three steps when he heard the clink of his nailed boots against something on the floor, which, by the sound, he thought must be metal. Stopping, he groped on the ground, and had just time to pick up something small and round, which he fancied might be a coin, when a stronger pull then before at the rope round his waist dragged him away, and told him that Sep believed him to be in some dire emergency.