Shann squirmed. That was, of course, a very obvious supposition. He kept a tight hold with his left hand, and with the other, he did some exploring. Yes, here was a hollow right enough, twin to those on the outside. But to swing over that narrow edge of safety and begin a descent into the black of the well was far harder than any action he had taken since the morning the Throgs had raided the camp. The green mist could hold no terrors greater than those with which his imagination peopled the depths now waiting to engulf him. But Shann swung over, fitted his boot into the first hollow, and started down. The only encouragement he gained during that nightmare ordeal was that those holes were regularly spaced. But somehow his confidence did not feed on that fact. There always remained the nagging fear that when he searched for the next it would not be there and he would cling to his perch lacking the needful strength in aching arms and legs to reclimb the inside ladder. He was fast losing that sense of well being which had been his during his travels through the fog; a fatigue tugged at his arms and weighed leaden on his shoulders. Mechanically he prospected for the next hold, and then the next. Above, the oblong of half-light grew smaller and smaller, sometimes half blotted out by the movements of Thorvald's body as the other followed him down that interior way. How far _was_ down? Shann giggled lightheadedly at the humor of that, or what seemed to be humor at the moment. He was certain that they were now below the level of the sand floor outside the slab. And yet no end had come to the well hollow. No break of light down here; he might have been sightless. But just as the blind develop an extra perceptive sense of unseen obstacles, so did Shann now find that he was aware of a change in the nature of the space about him. His weary arms and legs held him against the solidity of a wall, yet the impression that there was no longer another wall at his back grew stronger with every niche which swung him downward. And he was as sure as if he could see it, that he was now in a wide-open space, another cavern; perhaps, but this one totally dark. Deprived of sight, he relied upon his ears. And there was a sound, faint, distorted perhaps by the acoustics of this place, but keeping up a continuous murmur. Water! Not the wash of waves with their persistent beat, but rather the rippling of a running stream. Water must lie below! And just as his weariness had grown with his leaving behind the fog, so now did both hunger and thirst gnaw at Shann, all the sharper for the delay. The Terran wanted to reach that water, could picture it in his mind, putting away the possibility--the probability--that it might be sea-born and salt, and so unfit to drink.