Her mother whirled and drove her palm against Allel's cheek. Blood pumped into Allel's mouth and strange scents flooded her head.

"You've learned nothing," Boyd said hoarsely. "I'd rather leave you here." She forced herself forward, fists clenched white.

Allel mumbled: "I mean it." She felt blood freezing on her lip. She became aware she'd lost her cap. But Boyd was hesitating.

"How?"

"If I succeed..." She coughed and spat blood. It was vivid against the snow. "If I succeed, will you help me build a hyperdrive machine to fly to the Shell?"

Boyd's eyes narrowed. "I don't believe it. You're bargaining with me..." Then she dug a bark handkerchief out of a voluminous pocket. "Here. Clean yourself up."

The dozen warriors converged on the Bridge. They wielded branches hacked from cow-trees, their miraculous meat buds smashed away. To Allel, watching from above, the crude clubs were symbols of the depressing symmetry of humanity's rise and fall.

The Bridge was a gleaming parabola plastered with teepees. From the teepees defending warriors emerged, grubby and yelling, brandishing rocks and clubs. Blood splashed over the seamless carriageway. But soon it was hard to separate the two sides, but Allel could see that as before the attackers were being driven away.

The breeze picked up and the great balloon over her creaked into motion, its stitched bark straining. The canvas sling chafed her armpits, and she tended the alcohol burners clustered like berries just above her head. The balloon wallowed in the air. Soon its load would be lighter, she thought, uncertain of her feelings.

Her shadow drifted over the melee, touching fighters, men and women alike, who wriggled together like blood-soaked termites. They looked up in fear or anticipation. She took a small alcohol lamp, one of a cluster tied to her belt. She lit the lamp, cut its cord with her stone knife, and dropped the lamp delicately into the defenders' muddled line. The lamp flared into flame; a toy man ran screaming, his shirt a torch. Another lamp, and another. Cries of anger sailed up at her, followed by whirling clubs. No weapons could reach her, and she dropped her lamps. Then the defenders' line broke and the battle surged across the Bridge. Teepees crumpled, and old folk screamed. Allel thought she heard her mother shout in triumph.

Her lamps gone, Allel dropped the pouch and the balloon rose further. She stared up at the Shell's complex tapestry and waited for a breeze to take her home.

She found the teepee's air filled with her mother's sweat and dirt. Boyd's left wrist was a stump of torn blood vessels and shattered bone. It had been cauterized; now Lantil bathed it with milk and tears. Boyd took Allel's forearm in a grip that pulsed with pain. "Daughter! Your damn bag of smoke worked..."

Allel tugged gently, wanting only to be released. "Yes. And now you'll have to help me build a real machine to cross the Gap."