The navies of Helium and the First Born had cleared the fortresses and the temples of the therns when they had refused to surrender and accept the new order of things that had swept their false religion from long-suffering Mars.

In a few isolated countries they still retained their age-old power; but Matai Shang, their hekkador, Father of Therns, had been driven from his temple. Strenuous had been our endeavors to capture him; but with a few of the faithful he had escaped, and was in hiding—where we knew not.

As I came cautiously to the edge of the low cliff overlooking the Lost Sea of Korus I saw Thurid pushing out upon the bosom of the shimmering water in a small skiff—one of those strangely wrought craft of unthinkable age which the Holy Therns, with their organization of priests and lesser therns, were wont to distribute along the banks of the Iss, that the long journey of their victims might be facilitated.

Drawn up on the beach below me were a score of similar boats, each with its long pole, at one end of which was a pike, at the other a paddle. Thurid was hugging the shore, and as he passed out of sight round a near-by promontory I shoved one of the boats into the water and, calling Woola into it, pushed out from shore.

The pursuit of Thurid carried me along the edge of the sea toward the mouth of the Iss. The farther moon lay close to the horizon, casting a dense shadow beneath the cliffs that fringed the water. Thuria, the nearer moon, had set, nor would it rise again for near four hours, so that I was ensured concealing darkness for that length of time at least.

On and on went the black warrior. Now he was opposite the mouth of the Iss. Without an instant’s hesitation he turned up the grim river, paddling hard against the strong current.

After him came Woola and I, closer now, for the man was too intent upon forcing his craft up the river to have any eyes for what might be transpiring behind him. He hugged the shore where the current was less strong.

Presently he came to the dark cavernous portal in the face of the Golden Cliffs, through which the river poured. On into the Stygian darkness beyond he urged his craft.

It seemed hopeless to attempt to follow him here where I could not see my hand before my face, and I was almost on the point of giving up the pursuit and drifting back to the mouth of the river, there to await his return, when a sudden bend showed a faint luminosity ahead.

My quarry was plainly visible again, and in the increasing light from the phosphorescent rock that lay embedded in great patches in the roughly arched roof of the cavern I had no difficulty in following him.