Thorinn sat looking at the ruins of his work. He felt a sudden elation, and realized after a moment what it was about: he knew a way to get up through the cataract.
"Box, if it should rain here so long that the valley is flooded, will the waterfall keep on flowing or will it stop?"
"It will stop, Thorinn."
So it must be; the rulers of the world, whoever they were, could not be expected to take such care of their subjects, only to let them drown in a flooded cavern. Now his way was clear.
Only two panels of the bladder had been ruined by the lightning, which had run down them like a crooked river, burning away a channel nearly a span in width and leaving the edges blackened. Thorinn made new panels, fitted them into place, glued and dried them.
In one of the workshops he found a basket adequate for his needs: it was round, nearly two ells broad, and two spans deep. For a firepit he brought clay from the riverbank and formed it like a deep dish in the center of the basket, leaving a space half an ell broad all around for himself and his possessions, including the firewood and kindling he must take with him. The basket had four handles by which he meant to suspend it; for this purpose he knotted together a rigging to fit over the inflated bladder. He attached a long cord to the top of this rigging, and eight shorter ones at the bottom which he brought together and fastened to the four handles of the basket. He also cut some pieces of wall-stuff to use as patches in case the bladder was damaged.
Now he had to consider how to defend himself if he should be attacked by an engine in the tunnels. He filled bags of flimsy paper with pitch and bound them to the tips of the stoutest arrows he could find. The bags burst and splattered when they struck a target, but he was not yet satisfied. What he wanted was something to entangle the limbs of the engine. He thought of sticky cords bursting out of the bag—but if they were sticky, what was to keep them from clinging together?
He began again, using fishing lines which he coated with pitch and then coiled inside the bag. But the bursting of the bag did not carry them far; something else was needed. He thought of springes, and began to make small circlets of sapling branches, tied together with the thinnest thread. He fastened stone weights to the ends of his fishing lines and coiled them so that the weights lay against the ends of the circlets where they were joined. After many trials he discovered how to mix the pitch with just enough water and fish-glue to make the lines fly apart when the thread broke. In the end he had in each bag a complicated construction of three sapling-rings, each with its coiled and weighted cord, each set in a different direction. When he fired it at a tree, the sticky lines whipped out in all directions and tangled themselves among the branches.
He prepared ten of these pitch-arrows, and in addition took a quiverful of the ordinary kind. Now he was almost ready. "Box," he said, "show me what way the engine brought me down into the cavern."
In the crystal appeared the outlines of a slanting tunnel. It forked, and one passage went steeply up while the other continued at the same pitch for a little space before it turned upward and became a vertical shaft. A tiny dot descended this shaft, moved down the slanting tunnel, and disappeared.
"Show me where the water runs."
The first fork and the stem of the Y filled with shimmering blue. "And that second shaft?" Thorinn asked, pointing. "Where does it go?"
The outlines drifted downward in the crystal. The shaft rose through a vast space and continued upward. At the far end of this space there were other shafts.
"What is that, another cavern like this one?"
"It is a cavern smaller than this one, and it is different in other ways."
"Are there men in it?"
"No, only engines."
Thorinn frowned. "Show me these engines."
In the crystal, he was looking into a cavern full of confusing shapes. An engine drifted by, then another. They paused, touched the side of one of the huge shapes that rose around them, then went on, for all the world like bees gathering pollen. They did not look at all like the engine that had captured him before.
"Box, will they harm me?"
"No, Thorinn."
"And that shaft in the ceiling, where does it go?"
The view traveled upward, the lines shrank together, and he was looking at another maze of passages, shafts, and tunnels. "Will it take me back to the Midworld?"
"Yes."
How much of this could he believe? The conviction had been growing on him that the box was not to be trusted, and that if it had another chance to betray him it would do so. Well, he would see. Early the next morning, before the children were awake, he collected all his belongings, including the tightly wrapped bladder with its basket, and set out for the upper end of the cavern He built himself a little shelter of branches near the cavern wall, within sight and sound of the cataract, and lay there that night. On the following day he began cutting poles for a shed ten ells long, eight high, and four wide. He planted the poles on rising ground above the river, and lashed other poles to them to make a peaked roof. He thatched the roof with bundles of branches to the thickness of half an ell. In the middle of the space covered by the shed he dug a firepit, and on either side he stacked dry wood from the forest. Then with his sword he cut through the trunks of four trees, forming a rough oblong around the shed, at a height of fifteen ells. He notched the stumps and cut the logs into pieces six ells long, which he raised with much toil, using a rope and a tripod of poles, and set into place at the ends of the oblong; he notched these in turn, and now cut more logs fourteen ells long, which he laid across the structure to form a solid flat roof above the peaked roof of the shed; and with leather thongs filched from the wingmen's workshops, he lashed the whole structure firmly together. All through this work, which occupied him fourteen days, the air was cloudless.
On the fifteenth day he built a fire in the pit and touched it off. The flames mounted; smoke poured up under the roof, and Thorinn retreated to the shelter of a nearby tree. Presently the rain began; first a patter, then a steady hammering in the leaves above. Thorinn shut his eyes and waited. There was an earsplitting crack and a white glare that he could see through his eyelids. When he looked, he saw that the log roof above the shed was splintered but unbroken. The rain continued in a steady torrent. After a time, without warning, there was another lightning-stroke and a clap of thunder; again the roof was splintered—he could see the white spears standing up at all angles above it—but it held. The thatched roof beneath was not even touched.
Thorinn watched until the rain began to spatter from the overloaded leaves of the tree above him. He ran to the shed, stayed there long enough to bank his fire, and ran back drenched to his shelter near the cliff. All day long the rain continued, and at intervals peals of thunder rolled down the valley and the sky was lighted with a violet glare. Toward evening Thorinn pulled his shirt over his head for a cloak and went down to the river. It was swollen and white-capped, twice as wide as before. He went back to the shelter, ate his evening meal, and fell asleep to the drumming of rain in the treetops. Sometime during the night he woke up realizing that the sound had stopped. He ran to the shed and found that the fire had gone out, although the shed was intact and dry. He built the fire up again, waited as before until it was burning well, then banked it, and went back to bed. In the morning the river was a surging brown flood. Thorinn ventured out to the shed, found the fire low, and built it up once more. The log roof was a mass of splinters from the repeated lightning-strokes, but the splinters themselves, as he had hoped, made a roof almost as good for his purpose as the original. The river sprawled wider, creeping almost visibly up the slope; by now, Thorinn thought, it must be almost to the wingmen's towers.