"That is the forbidden research upon which Loki was engaged, and which caused us to banish him from Asgard," Thor explained. "Above that door is a tunnel connected with the sea of the upper world. If the door were opened, sea water would rush down into this underworld."
"Good lord!" I cried in horror. "If sea water ever poured down into this world of fire, there'd be an explosion that would shake the planet!"
"Aye, and Odin saw that danger," Thor said. "Loki planned to admit only enough sea water to produce the titanic power of which he had need in his experiments. But Odin pointed out that if anything went wrong — if this door were completely opened and the sea rushed down unchecked into Muspelheim — there would be such an explosion as would rend the whole land above. It was the reason for Loki's banishment."
As Thor spoke, he was moving the control lever. The floating disk began to rise in the vertical shaft, out of the fiery underworld. With all the tiny valve-doors closed, it rose quickly under the pressure of the powerful radiation. We shot up the dark shaft at a speed that almost equaled that of our descent.
We were none too soon. A savage pain in my back told me that the radiation had just been starting to penetrate my weakened protective garment. Already it had scorched my flesh!
Clinging to the rocking, rising disk, I held the crucible to keep it from sliding away. The radioactive matter in it shed a feeble glow upon the dark walls of the pit as they raced downward. Then Thor slowed our rise, and finally the disk came to a halt at the mouth of the shaft. Again we were in the torchlit chamber under Valhalla castle.
Odin was awaiting us. The Aesir uttered an exclamation of relief as Thor and I stumbled off the disk with the crucible and removed our stiff garments.
"Lord Odin, I fear we didn't get all the radioactive fuel you'll need for your mechanism," I said bitterly. "It was my fault that we were forced to leave—"
Odin looked with a shadow of worry in his eye at the half-filled crucible. But he spoke confidently to me.
"It should be enough, Jarl Keith, to defend us from Loki's storm weapons. See, I have converted another mechanism into such a generator as we will need for that defense."
The mechanism was concealed by a spherical copper cover upon which was mounted a smaller copper ball. There was a hopper in its side, into which we poured the chunks of glowing mineral.
"It should have power enough to maintain a defensive screen against the force of Loki's storm-cones for a short time," Odin said. "If he should use the storm-cones for longer than that—"
He did not finish, but I shared the deep worry that was etched in his strong face.
"I saw Loki's handiwork below," I said, and described the sliding door in the roof of the fire-world, which Loki had designed to admit sea water. "No wonder you cast Loki out for such a terrifically dangerous plan."
"Aye, it was Baldur who discovered that plan, and was slain by Loki for exposing it," Odin said somberly. "Loki had perfected a remote control for that sliding door, operating by tuned vibration. Here it is."
And Odin showed me, among the many dust-covered instruments in the chamber, a small, square silver box. On it was mounted a knob whose pointer could be turned along a semi-circular scale.
"Turning this knob would open the sea-door a bit or wide," the Aesir king said. "When Loki fled from Asgard, he took this control box with him. And when we trapped him in that cave below Midgard, and we were about to kill him, Loki threatened to open the sea-gate wide and destroy us all. That was why we had to agree not to kill him, if he would surrender this control box to us. He did surrender it. We kept our word and did not kill him, but placed him in the suspended animation in which he lay for so long."
Odin went to the door and called up through the corridors for some of his thralls to come. When they came, he bade them carry out the big spherical copper generator.
"We shall place it on Vigrid field, on the mainland across Bifrost Bridge," he said, "and keep it under guard tonight. For it is there that we must make our stand against Loki's forces when they come in all their fury."
He, Thor and I followed the thralls as they bore the heavy mechanism through Valhalla castle and out into the windy, gusty night. Torch-bearing thralls went ahead to illuminate the way. Lights shone from all the castles of Asgard. The Moon was hidden by driving clouds as we moved in a little torchlit group across the giddy span of Bifrost to the flat field on the opposite promontory,
My plane was still where I had landed it. Aesir warriors and mounted scouts were on guard, watching toward the south for the first approach Of Loki and the Jotun horde. As Odin directed the placing of the copper mechanism, I went to my plane. Something had occurred to me which might enable me to devise an additional weapon for the coming battle.
In the plane were the half-dozen big signal rockets which were to be used in case I made a forced landing and had to summon help. I began taking the rockets apart, pouring out the gun powder in them, and carefully unfixing the detonators. At the end of a half-hour, I had made three crude hand-grenades or small bombs. I hoped they might be of some use against the Jotuns, who knew nothing of explosives. I left the bombs in the plane and emerged to find Thor waiting for me.
"My father has already returned to Asgard," the Hammerer told me. "And it is time we followed him, for our nightly Valhalla feast begins soon."
"Thor, what of tomorrow's battle?" I asked. "If it comes to sword and spear, with the Jotuns outnumbering us many times, what can we do?"
"We can triumph or we can die!" boomed the giant. "And if it is death — well, the Aesir have lived long and are not afraid to die, so long as we take our enemies with us." He tossed his great hammer in the air and caught it in outstretched hand, as though it were a willow wand. "Be not impatient, Miolnir. You'll not thirst long. And now to Valhalla, Jarl Keith."
Valhalla was blazing with torchlight when we entered it. Logs in the great hearth burned high. In the flickering torchlight, all the captains and great warriors of the Aesir were gathered at the many tables. The Aesir nobles were appearing, striding toward the high table on the dais. I took my place beside Freya. Beyond her were the two empty seats of Frey and Gerda, then Bragi and Idun, old Aegir and his wife, and brooding, silent Tyr.
Odin and Frigga entered, and we all stood up. The Aesir king's eye surveyed us with stern pride.
"Be seated, jarls and captains," he boomed. "Let us eat and drink as of old. Though war and death surge upon us tomorrow, yet is there no fear in our hearts."
"Skoal to Odin!" rang Forseti's deep voice.
We seized our drinking-horns and raised them high to a crashing shout of confidence and pride.
"Skoal to the king!"
We drained the mead and sat down. The tall serving-maidens hastened to bring us more drink and meat. The din of voices and laughter rang forth, loud as ever. The deepening shadow of dire disaster which lay over Asgard that night intensified, rather than lessened, the merriment of the feast. Horn after horn of the sweet, potent mead we drank.
Beside me, Freya's blue eyes clung to my face. The shadowed tenderness and love in them was more heart-stirring to me than all else.
"Come good or ill, Freya," I whispered, "it is worth having lived to sit here tonight with you and your people."
"Aye, Jarl Keith," she replied. But there was wistfulness in her voice as she added: "I would that I could foretell our sitting here again tomorrow."
Suddenly all the cheery voices died. Into the hall strode tall Heimdall, warder of Asgard's gates.
"Why are you here, Heimdall?" Odin asked. "Is it not your task tonight to watch over Bifrost Bridge, and sound the great blast on Giallar horn when the enemy approaches?"