"To save the world?" The old woman smiled, not unkindly. "Yes, just like I was... or," she continued, "perhaps you are a bit tougher. I crossed the Gap with my mother -- that was adventure enough -- but I'd never have dreamed of challenging the Sun itself..."

Allel's rheumy eyes peered into the wavering light of a lamp. "There are so many differences between Home and Shell. We had no mummy-cows to feed us, you know. Only cow-trees. And we spoke a different language. It took me long enough to learn yours, I can tell you, and my mother wouldn't even try...

"I wonder if all these differences were intended, somehow. Perhaps the Sun was meant to fail. Perhaps there's a plan to force us to cross the Gap, to mix our blood and toughen ourselves--"

Teal pushed away the knife and lay back on his rustling pallet. He'd heard all this before. "Maybe, but such speculation won't help us find a way out of the trap the world's become. Will it?"

Allel shrugged mildly. "Perhaps not. But the alternative is ignorance -- which can only drive you to spectacular suicide. Such as by crashing into the Sun in a leather balloon."

Teal found himself blushing under his blisters.

"Before you can find a way out of the world you need to understand its nature." She wagged a bony finger. "Are you prepared to be a little patient, and do a bit of thinking?"

Teal smiled and propped himself up on one elbow.

Allel put aside the bowl of broth and settled herself onto a mat beside the pallet, cross-legged. "When I wasn't much younger than you, my mother took me on a long walk to an old abandoned City to the north of Home. And there I learned something of the nature of our world.

"The world is a box. We locked ourselves into a huge box to escape from the Xeelee, whatever they are. But the nature of this box is quite remarkable."

Teal gathered the blanket tighter around his aching chest. "Go on."

Allel pulled up a section of the leather mat beneath her and bunched it into a rough globe. "Here's a model of the world. Let's imagine there are insects living on this globe." Her fingers trotted comically over the globe; Teal smiled. "They're perfectly happy in their little world, never imagining the mysteries above or below them. Yes?

"Now. I think the world we came from is a flat place, somewhere... else. Just like the rest of this mat -- a flat place that goes on forever, and contains stars and Xeelee."

She pointed at the place where the globe joined the mat, encased in her spidery fist. "The worlds must touch, as these models do here. We have to find such a place. A place where you can walk out of our world and into the original... a door to fold through."