“The Pons Absconditus isn’t much farther,” Inessa said. “Well, I mean, it’s all over the place. But one fairly constant anchorage isn’t much farther. We’ll get you there and that little wisper won’t have a chance to get near you again. Then the Propheseers will explain everything. They’ll show you the book.” The UnSun was gone, and Zanna and Deeba pulled themselves, exhausted, over the roofs. The Slaterunners surrounded them closely now, kept watch on all sides.

“What book?” Zanna said.

“I’ve never seen it,” Inessa said. “Not many people have. But you hear things. It’s big. It’s old. It’s thick, bound in devilhide and printed in kraken ink. But that’s considerably less important than what’s inside.”

“Which is?” said Zanna.

“UnLondon. The history, the politics, the geography. The past…and the future. Prophecies.” She looked at Zanna. “Prophecies about you.”

Zanna looked thoughtful. The two girls stared back at the motionless fireworks of the November Tree behind them. “You do realize,” said Zanna, “that you’re stroking a milk carton.”

“You’re just jealous,” said Deeba. She was holding Curdle in one hand, gently rubbing it with her other. “’Cause it’s the one thing here more interested in me than you.”

“I am jealous,” said Zanna. “That is exactly it.”

They were tired and hungry and homesick, and Hemi’s sudden appearance had frightened them.

“It’ll be alright,” Zanna whispered.

“I wonder how Obaday and the conductor and that lot are doing,” Deeba said. “I hope they got away from the flies by now.”

“Oh,” said Zanna. “Yeah. I hope.” Deeba looked at her suspiciously.

“You hadn’t thought,” said Deeba. “You’re too busy thinking about what’s in that book.”

Zanna said nothing.

They crept on through the ivory loonlight, Deeba and Zanna miserable with exhaustion. After a long time climbing, Deeba realized that Curdle was shifting in her hands, sniffing, whiffling, and puffing with its opening.

“Zann,” she whispered.

“What?”

“Listen,” Deeba said. “Curdle’s being funny. Something’s…” The two girls stood still a moment, motioned the Slaterunners to stop, were silent.

Faintly, from behind them, they heard a pattering.

It came closer. Something was approaching, was only a few streets away, below them.

“It’s him again!” whispered Zanna.

“But…it’s too heavy…” Deeba said. “And there’s more than one…”

“Footsteps.” The two girls jumped as Inessa slid in between them and hunkered close to the roof, her ear to the slates. “Someone knows you’re here. They’re coming.”

“He must’ve been a spy,” said Zanna. “He’s sent them after us…”

“There was that weird bird, too,” Deeba said.

“Jonas, Alf,” Inessa said to two strong-looking Slaterunners. They squatted by Zanna and Deeba, offering their backs. “Hang on,” Inessa said.

“You must be joking,” Deeba said.

Inessa pointed.

Several streets away, dark shapes were bobbing above the gutters. Heads in strange masks jutted into the roofworld itself.

“Oh my God!” Zanna said. “They’re giants!”

“Quickly,” Inessa said. “The rest of the tribe’ll delay them, but we’re going now. Hang on.”

Zanna and Deeba felt the lurch of their carriers, the faint huffs as they cleared clay and slate, the long moments of soaring as they jumped over the gaps of streets.

“Help,” Deeba wheezed, her eyes clenched.

Behind them was a sound of shattering tiles and the phut s of blowpipes as the Slaterunners ambushed the intruders.

“Who are they?” Zanna said as Jonas roofran.

“Know who…you are…” Jonas said between breaths. “Must be…with the Smog.”

“Keep going,” said Inessa. “They’ve got up here.”

Zanna opened her eyes. Strange figures silhouetted against the sky, approaching steadily across the roofs.

“Deeba,” she said. “They’re coming after me.”

“There’s nothing for it,” Inessa said after a moment, sounding despairing. “We’re going to have to…descend.”

“No!” said Alf and Jonas.

“We’ve no choice!” Inessa said. “They’ll never expect it. It’s the only way we’ll lose them.

“Three generations,” she said wistfully. “Well…Anything for the Shwazzy. Follow me! ”

She ran to the edge of the roof. She leapt, somersaulted, plunged towards the street below…

…and landed almost immediately. She stood up. Her head was only a little below them.

Jonas and Alf dropped off the roof. The pavement started just inches below the eaves. The roofs slanted directly up from the ground.

“Where are the houses?” said Deeba.

“What houses?” Inessa said.

Deeba and Zanna stood in the little alley, embedded with the bulbs of streetlamps, staring astonished at the roofslopes they had just left.

“I can’t believe it!” Deeba said. “Even if you fall off you’ll only scrape your knee.”

“You thought there were houses under the roofs?” Inessa said. “That would be madness! Just because we want to live free doesn’t mean we shouldn’t consider safety…”

“The people following aren’t giants at all,” Zanna realized.

“On which topic…” Jonas said.

“Yes, now’s not the time,” Inessa said. She gestured, and she, the Slaterunners, Zanna, and Deeba dropped to their hands and knees and rolled into the tiny space below the eaves.

They waited, then froze when they heard bootsteps overhead.

There were hunters on the roof above them. It sounded as if they were milling from one corner to another, poking into shadows. None spoke.

Deeba held her hand over Curdle’s opening, so it could not whimper.

For a horrible moment one of the unseen figures was directly above them, so close the guttering shook by Zanna’s head. She and Deeba stared at each other, their eyes very wide. None of the Slaterunners, nor either of the girls, dared breathe.

At very long last, the searchers moved away. Zanna let out a trembling sigh. Silently, Inessa beckoned and crawled on.

What seemed like hours later, they reached the edge of the Roofdom.

Zanna and Deeba emerged from under the eaves. Before them, the streets sloped away, and the real walls of UnLondon rose, in bricks and wood and the mixed junk called moil.

“Not far now,” Inessa said. Alf and Jonas trod gingerly, and grumbled about how much they hated it down on the ground.

Behind them, the roofs sloped directly up from the pavement like slate tents. Zanna and Deeba rolled their eyes.