Deeba crept up the stairs, the UnGun raised. Lectern came hesitantly behind her, carrying the book. Curdle jumped energetically from step to step.

“Come on,” the book whispered to Lectern. “Keep up, keep up.”

After several twisting flights, they reached the top. At the end of the hallway was a door, from above and below which Smog oozed.

“We better be fast,” Lectern said. “This Smog’s going to sense us any minute.”

The corridor shimmered in the vivid colors of night. One whole wall of the passageway was windowed.

“Look at that,” breathed Lectern.

They stared out onto UnLondon at war.

There was the streetlamp glow, rising where the inhabited boroughs were, and between them the coiling dark of smogmires. But that night, UnLondon was also flickering in the illumination of many fires. There were the flashes of combustion, and the glowing beams of flashlights from the streets, from the dark cut of the river, where they danced with their reflections, and coming down from the sky, from aircraft and other flying things, racing in all directions.

“It’s kicked off,” said Deeba. “It really has.”

She could hear the sounds of battle.

“Look,” she said.

Below the rising and falling roofscape of the floors below them, they could see the factory forecourt. It was full of a huge fight. Behind the walls and thrown-up barricades, and on roofs to either side, battalions of smombies threw missiles. Stink-junkies pumped smoke and fire.

The attackers, just beyond the entrance, were the UnLondoner troops that had gathered with Deeba by the river.

They fired weapons and swung grappling hooks over the walls. Many wielded big fans, and swung them like axes at the Smog as it approached, blowing its smaller clots away. The dirty smoke scattered, gathered again at the edges of the yard, and re-formed for counterattacks.

“Un Lun Dun!” Deeba heard the rebels shout. “Un Lun Dun!”

“There are more of us than there were by the river,” Deeba said. “People are joining.”

“But most UnLondoners still think Unstible’s on their side, don’t they?” Lectern said.

“Maybe not, not round here. As soon as they see he’s using smombies and that, they’ll know he’s with the Smog. In fact…”

“In fact word of that’ll spread,” the book finished. “And Unstible must know it. So it’s decided, whatever it’s going to do…tonight’s its last chance.”

“But that wasn’t their plan. ” Deeba frowned. “The whole thing I heard them talk about…it was all about how people would think Unstible and Brokkenbroll were on their side, and that’s why they’d do what they were told. Why’s he giving it away?”

“Maybe they’re desperate,” the book said uncertainly.

“Look,” said Lectern. She pointed.

Among the vessels, birds, bats, grossbottles, and smogglers racing through the sky was a cluster of shadows. It was flying in a strange way. It was a dense mass surrounded by outriders. It careered towards them as chaotic and lurching as a crowd of moths, coming at tremendous speed.

“What is that?” whispered Lectern.

Specks flew up from the city as the mass approached, and joined it, and others dropped away from it and torpedoed into the streets. Deeba saw one of them fold its wings and fall like a crooked, hook-ended missile.

“Uh-oh,” she said, and stepped back from the window. “It’s the unbrellas.”

In the unbrella flock’s dark center, something dangled like an ugly fruit.

“Brokkenbroll,” Deeba breathed.

The Unbrellissimo was holding on to one of the unbrella’s handles, hanging below it as it opened and closed. He swung and reached with his other hand, grabbed another of the unbrellas. Again and again, he moved like someone on monkey bars, hand-to-hand, as if clambering his way through the sky. The unbrellas carried him each in turn.

The swarm swept into the factory’s yard. They spread out among the fight. Then to Deeba’s surprise they each flipped around, hovering in front of every woman or man, offering their handles.

“Friends!” Brokkenbroll shouted over the noise of the battle, dangling like a lunatic Mary Poppins. “It seems, uh, the Smog’s forces must have managed to get into Unstible’s factory. I’ll make sure he’s unharmed. It’s heroic of you to rush to his defense like this. I’ll check on him. In the meantime, I notice that none of you have unbrellas. The Smog’s attacking all over! Please, take them! They’ll protect you!”

Some of the rebels looked at each other in confusion. A few reached hesitantly and took the unbrellas flapping in the air before them. But even as Deeba began to hammer on the window and shake her head, she saw people smacking the unbrellas out of their comrades’ hands.

“Are you mad?” Deeba heard one say.

“We know what you’re about,” shouted another. “Enough of your lies! Un Lun Dun!” He hurled a half-brick, and Brokkenbroll had to sway out of the missile’s path.

The Unbrellissimo’s face lost its expression of anxious concern. A look of rage replaced it. He bared his teeth and growled.

“That girl !” he shouted. He swept his free arm, and his unbrellas attacked. They reared and clubbed at the UnLondoner troops, joining the smombies and stink-junkies.

The Unbrellissimo rose to overlook the scene, and very suddenly, he was at the level of the window, looking straight at Deeba.

“Uh-oh,” she said, and moved back from the glass. It was too late.

Brokkenbroll opened his mouth, and pointed at her.

His unbrellas hauled him, hand over hand, straight for her. His coat flapped. He loomed.

Like bugs on a windshield, unbrellas hurled themselves at the windows, cracking and bursting the panes.

“Come on!” said Deeba. Lectern couldn’t take her eyes off the oncoming Unbrellissimo. She would have dropped the book on the ground if Deeba hadn’t caught it.

“I said come on !” said Deeba. She grabbed the book under one arm, tucked the UnGun in her trousers, and pulled Lectern along. Deeba dragged her down the passageway towards the Smoggy door. Curdle scampered after them.

Eddies of Smog tangled around Deeba’s feet. They were thick enough to feel like cotton wool. She stumbled.

It didn’t make any difference. There was no way she could have crossed the distance before Brokkenbroll arrived.