He got up and made his preparations. He filled a sack with enough food for several days. He took his homemade canteen, made from a hollowed-out Moontree fruit rind, filled it with water and hung it around his neck. He took his flashlight and knife, his bow and arrow, and his lantern of light organs. He had discovered that the little light-giving bulbs the animals carried would glow for about two days after their removal, and therefore he constantly kept this lantern refilled with his latest catches.

He looked to see whether his special lot of penned rabbits had enough food and water for the period and then, whistling to Cheeky, Robin set out. He went down to the bank of the flowing stream on which he had been originally carried and then set out to follow this rivulet its length into the distances of the bubble-world.

He followed the flowing stream for about twelve miles. The bubble widened out and the water, which had originally brushed the other side of the cavern where Robin had lived, had now narrowed as a bank of dry ground formed on the opposite side. Robin found himself walking through an ever deepening thicket of growing Moontrees which went on for many miles.

The stream twisted and moved off at right angles finally rushing into a deep pool. Robin went over and gazed into it. Plainly the pool had some sort of underground opening, for the water was swirling around with no visible surface outlet. So this was where the stream ran to! Doubtless it emptied into another bubble somewhere below, probably to fall like a waterfall into that space, there to become another stream and empty still again farther down until it ended in some vast reservoir of sublunar seas.

But Robin was not interested in going farther down, he sought a way upward toward the surface, toward the sight of Earth. He turned away from the whirlpool, walked boundingly on to the farther wall of his home-bubble.

He reached it in time for his sleep period. It seemed as solid and impregnable as the wall around his home region.

Robin and Cheeky slept next to the wall and after their sleep resumed their search. Robin walked along the wall, looking again for some break. He saw in the distance a jagged line of black against the shining brown-gray of the cliff. When he reached it, it was a crack, a break in the surface of the bubble, reaching up several hundred feet. He came up to it.

It was wide, about ten feet wide, and dark. Robin shone his flashlight in, but as far as its rays could reach it was a dark tunnel. "Maybe this is what we're looking for," Robin said to Cheeky. "It seems to slant slightly upward. Maybe it will take us to the next bubble."

Cheeky peered in, walked in slowly and out of sight. "Hey," called Robin, "wait for me!" He followed the scampering monkey.

Now his lantern proved handy. The glow it shed could barely be noticed in the light of the great bubble, but here in the darkness of the cleft, the pale glow was distinct and definitely illuminated the ground a few feet in front of him. On he walked, holding the lantern ahead of him, watching Cheeky's long tail flick in and out of its circle of dim light, as the monkey would dash ahead and dash back.