This revelation was the last thing Hayden had expected from Aubri. He tried to imagine some alien machine coiled in her throat, watching him through the veil of her skin. The thought made his scalp prickle. "So what's this mission?" he asked after a long silence. "I can't tell you," she said simply. "It might activate." Confused and upset, he followed her to a cage mounted on one wall. There perched a bored-looking woman with arms like birds' legs, her prehensile foot crooked around a strap while she filed books in various slots in the cage. "Can I help you?" she asked, looking down her nose at Aubri.

"Hello, I'm not from around here. I'm looking for information about Leaf's Choir."

The woman's face brightened. "My, what an interesting accent! Well, welcome to Gehellen. And welcome to the library. Did you know we've been continuously open now for two hundred forty-seven years?"

"That doesn't surprise me at all," said Hayden.

"What about Leaf's Choir?" Aubri asked.

The librarian yawned. "The novels start over there, and wrap halfway around. Children's stories over there. Opera and plays, there."

"What about aereography?"

"Maps? That would be that section there." She pointed to the opposite side of the room. "But you won't find much, comparatively speaking. Leaf's Choir is much more interesting as a story than as a place."

"Why's that?"

"It's just a burnt-out shell now. Nobody can go in very far because of lack of oxygen, and occasional flare-ups. And whatever was in the outer layers was stripped decades ago. Leaf's Choir is a sargasso."

Suddenly Hayden understood. The extra fittings on the Rook weren't just for winter travel; they included air tanks and sealant for the portholes. The ship had a furnace but it also had a rock-salt battery for storing heat.

We're going in there, he thought, in sudden wonder.

"It must have quite a history to be the subject of all those novels," said Aubri as she gazed at the stacks. The librarian nodded.

"The original story's as fabulous as the novels," she said. "Once upon a time, two suns burned in the heart of Leaf's Choir. The suns were invisible from outside the nation because they were surrounded by a single, vast forest: millions of weightless trees connecting and reconnecting like the threads of a spiderweb through an intricate network of lakes and rock bits. The forest made a sphere over fifty miles across and within it were dozens of towns and hundreds of villages built out of the living branches of the trees." The librarian shaped the forms with her hands, long shadows cast by the lamps interpreting her gestures on the bookshelves behind her. "The impenetrable barrier of foliage provided protection as well as wealth to the citizens of Leaf's Choir, and they prospered.

"After centuries of peace, rumor began to circulate of the beauty of an heiress from Leaf's Choir, and that rumor attracted the attention of a warlord who determined to have her for himself. He laid siege to Leaf's Choir and was finally able to seize the giant air-pumping stations that kept the forest from supersaturating itself with oxygen. He threatened to blow up the stations unless the young lady was turned over to him. The government refused but the heiress secretly fled the capital and made her way to the warlord's encampment, and there gave herself up.

"To punish the nation, the warlord ordered the pumping stations blown up. Then he left—and behind him, the millions of trees of the forest continued to bask and produce oxygen. Leaf's Choir had cultivated them for centuries, to the point where it needed the artificial circulatory system of the pumps to ensure that oxygen did not build up to dangerous levels within the nation. Without the pumps, the least spark might set off an impossible conflagration—and so it happened, weeks after the warlord left. The fire raged out from the heart of Leaf's Choir and consumed everything, town, tree, and sun. All that was left when it was over was a sphere of charred wood and ash thirty miles across. That sphere is now tethered at the edge of Gehellen's territory; we've been mining it for its charcoal for centuries. It's very slow work because the heat of combustion is still trapped in airless pockets deep inside the sargasso. If oxygen reaches them, they break into flame again; so Leaf's Choir remains choked with stagnant, dead air. We have special ships that can go in, but navigation is a nightmare; it's all just black twisted wreckage that goes on forever. Leaf's Choir is ugly now—like a scar on the sky. Nobody goes there, unless it's for mining."

"That's very sad," said Aubri.

Yet somewhere deep inside it, Hayden mused, was the hidden treasure of the pirate king.

They spent several hours poring over maps of the place. The librarian was very helpful—Hayden and Aubri were a blessed break in her routine, it seemed. They both began to relax in each other's presence again. Hayden couldn't help but be distracted by occasional flashes of thigh or calf when Aubri reached for something; she pretended not to notice him noticing. The time went quickly.

Still, Hayden couldn't stop thinking about the assassin thing she had described. He wondered whether there were some way to pull the monster out of her, or poison or blind it. Aubri spoke no more of it, and he said nothing further about his own troubles. Perhaps out of a mutual need to turn their thoughts away, they focused with great intensity on comparing photos of Venera's map to the various charts. The charts were all centuries out of date. As the librarian had pointed out, the outer shells of the sargasso had been stripped away long ago, and the inner ways were char. It would take a miracle of navigation to find the treasure.

"I wish Gridde were here," Hayden said eventually. "He'd be able to sort all this out." As he said this he realized he'd felt a pang of affection for the crabby old man. Well, why not? Gridde was no soldier, he was just in love with his work. He was an innocent.

Finally they had compiled enough information to satisfy Aubri. "I think we've earned a break," she said. "There should be a restaurant near here, don't you think?"

They followed the librarian's instructions and soon found them-selves back in the crowded sky of Vogelsburg. Distant Candesce was cycling into its evening phase, its light reddening slowly. Where the librarian had directed them, the air was so crowded with structures as to be nearly impassable. Blocks and spheres, triangles and loose basket-farms were jammed in together, all jostling for sunlight and air. People sailed every which way, and as they nearly collided they would reach out to push off from one another without rancor or pause. The air was full of the scent of cooking and of waste, as well as shouts and laughs overlaid with the distant, ever-present rumble of buildings grinding together.

Hayden had just spotted the wicker restaurant the librarian had recommended when suddenly Aubri clutched his arm. "Someone's following us," she murmured.

He restrained the urge to turn and look. "Are you sure? How can you tell in this crowd?"

"Because he followed us into the library. I spotted him dawdling in the history room when we were working. He was trying to see the maps, I'm sure of it. Now he's behind us again."

"Well…"

"He looks like one of them." He looked at her blankly. "One of the pirates!" she whispered.

Now he did contrive to glance casually behind him. Hayden spotted a shock of yellow hair moving through a swatch of sunlight and felt his scalp prickle with recognition.

"Come on." Hayden led them in a complicated path between buildings, just to see if their tail would keep up. He did, a constant in the churning flow of faces and clothing.

"Okay, forget about lunch. We'd better get back to the bike and tell the others about this." He grabbed a municipal rope to change his course; less gracefully, Aubri followed.