"We must get back!" he cried. "Even if we escaped, we two could not turn off that great sun-ray, could not wreck all its twenty controls. But if we could only get back to Earth and lead back here the fleet of space-fliers that the World President planned to build!"

"It's hopeless, Marlin," I said. "We've thought of a thousand ways of escape in the days that we've been here, and not one has even the wildest chance of success."

Hopeless indeed it seemed to Marlin and me as we sat there silent in the dusky little cell. For the colossal epic of Neptune's past and mighty plan which we had heard there from the Council of Thirty, from their globe-mechanism that centralized their minds, had implanted in us a profound despair. We had found at last the explanation of all this vast enigmatic thing that was wrecking our universe, but had found in that very explanation new depths of hopelessness. Earth was doomed, the solar system as such was doomed! We saw it, now, beyond all doubt, we, who alone of Earth's races knew whence that doom was coming. And I think that neither Marlin nor I, sitting silent there in the dusk of our cell, gave any thought to the terrible fate that hung over us two who had been kept alive, as we now knew, for whatever possible knowledge we might be able to impart to the Neptunians. We forgot our own fate of a living death amid the Neptunians in our agonized contemplation of the great deepening shadow of doom that was darkening the sun and all its universe.

It seemed to me, as we sat there, that it was centuries, rather than weeks, since Marlin had given to Earth his first warning of that doom, his first news of the sun's increased spin. All that we had come through since that time seemed the events of countless years. The great meeting of the World Congress, and its adoption of the plan of Marlin and Whitely; the building of the space-flier and that start by night of Marlin and Randall and Whitely and myself in it; our hurtling flight out from Earth on our great mission, past Mars and through the dangers of the asteroidal belt, past mighty Jupiter and on, spinning through the peril that almost annihilated us at Saturn, to our goal, Neptune; our amazement at finding that world roofed and enclosed, the venture of Marlin and myself down into its dead and deserted compartment-city; the attack of the Neptunians, the pursuit and destruction, somewhere out in the mists of Neptune, of our two friends, of Whitely and Randall in the space-flier; and our own capture, our own journey to Triton's swarming, strange world, and our days' imprisonment; and now, at last, this titanic tale of the past and purpose of Neptune's races, which had been told us by the great globe of the Council. It seemed incredible, indeed, that all of these things could have been so compressed into the time of a few-score days as they had been.

Yet they had been, I knew, and knew too that the sixty-odd days that remained to us before the end came, before the sun, spinning ever faster beneath the pressure of the giant ray from Triton, split at last into a double star, that these three-score days would seem centuries on centuries of agonizing torment for us two, who must wait, imprisoned here, for the doom that was closing down upon the solar system to come to its dread climax. And at that thought, at the thought of that helpless inaction that must be ours, a blind unreasoning revolt arose in me as in Marlin, and like him I sprang to my feet, paced the little cell's length with clenched hands. All was unchanged about us, the towering black walls around us, the half-heard staccato voices of the Neptunian guards outside, the dim roar of sound that came to us through the twilight from Triton's swarming sunward side. The very changelessness of the things about us pressed upon my spirits with such suffocating force in that moment, that I was almost on the point of beating blindly against the cell's door, when recalled to myself by the suddenly tense tones of Marlin's voice, beside me.

"Hunt!" he exclaimed. "There is a chance to get out, I think! I've been thinking, and if we can make a great enough effort I think that we can win clear of this cell, at least!"

I shook my head. "It's no use, Marlin," I said. "We've gone over it all a thousand times—there's no way out but through the door, and that never opens but with a half-dozen Neptunian guards standing with ray-tubes outside it."

"But there is another way," he persisted. "Out the cell's top, Hunt, out the roofless top!"

"We tried it," I told him, "and it was useless. Even with the lesser gravitation here on Triton, even without these weights on our feet, we could only jump a score or more feet straight upward, and the walls are two hundred feet high and utterly smooth and vertical."

"But one way we didn't try," he insisted, and as I listened with dull lack of interest, he went on to outline to me his idea. And as I listened, my indifference suddenly vanished, for I saw that Marlin's keen, inventive brain had really found a plan that would give us a chance of escape. "It's our one hope," he finished, "and if we can use it to get out of this cell, we'll have a chance to steal one of these cylinders of the Neptunians and get back to Earth in it in time!"