Boyd grunted. Sensitive to her daughter's mood, she drank in silence. She probed at her limbs. "At least we're still whole," she rumbled. She looked about. Then -- unexpectedly -- she grinned. "So we failed, did we? Eh?"

She dug her good hand into the ground, and then shook it in Allel's face. "Look at that! Look!"

At the heart of the clump was a bright orange flower. A Shell flower.

Allel's thoughts swam like fish. "Now I really don't understand..."

"We made it. We're on the Shell! That's enough for me." Then Boyd followed her daughter's gaze upwards, to the roof over the world. Her eyes narrowed.

Allel said slowly, "Above us we see Home, not the Shell. Yet it looks as the Shell does. The two worlds are complete in themselves, yet they are -- wrapped around each other. Symmetry. You see the same thing -- a Shell -- from whichever world you're on."

Boyd nodded shrewdly. "Well, that much I understand. Like us, eh? Two halves of the same whole. No weak center, no protecting Shell. Just the two of us."

Allel dropped her eyes, hotly embarrassed. She went on doggedly: "But how? If we're on the Shell, why doesn't the land curve up like a saucer? Why don't we see Home floating up there like a ball? How can it look like another Shell?"

Boyd made a little growling noise, and flung the shard of burner into the grass. A small flock of ice-blue birds clattered off, alarmed. "Well, you're the dreamer. Dream up an answer."

Allel lay flat. She rested her head on very ordinary loam and stared up through two layers of clouds. She thought of two worlds, each a ball yet each cupping the other like a shell round a nut. How could that be?

Her vision of her universe was crumbling, like the flaking planet-in-a-box milk painting on that museum wall. She imagined reaching into the box to the truth--

Boyd said gruffly: "Well, what now?"

Allel gestured vaguely. "Fix the balloon and get home. We've got to make people understand. Build more balloons and go to the old Cities. Find a way to turn back the glaciers, or fix the Sun..."

Boyd was staring past her shoulder. Allel turned -- then sat up quickly.

The boy stood at the edge of the stand of cow-trees. He was no better dressed than they were; teeth flashed in a dark face as he jabbered at them, smiling and pointing and cupping his hands.

Allel watched, baffled. "What's he saying?"

Boyd bellowed with laughter. "I think he's asking what it's like living in a saucer."

Boyd stood up and, with some dignity, straightened the shreds of her quilted jacket. Allel got to her feet, stiffly. "Come on," said Boyd. "Let's see if his people can cook as well as your grandfather."

They walked towards the boy across the meadow of bright orange flowers.