The women of Holloway emerged into Spike with their governor walking on the end of a rope. With Jan Burridge a hostage, the Riot Squad had fallen back, unwilling to provoke the rioters further. There were just too many of them. Attacked head-on by the women and from the flank by the men, they were overwhelmed in minutes. They fired off some rubber bullets – one took out a man’s eye – but when they lost their guns, it was all over. Burridge was pushed forward, a trophy prisoner.

Gripping the railing on level six, Ant spotted Tess Clarke. The woman she had last seen chained to her bunk now aimed a shotgun straight into Burridge’s bloody face.

‘Ant, there’s two more levels up here.’ Mattie was tugging his sister away from the railing. ‘We need more on our side. Let’s get everyone out.’

Ant tore herself away and followed him to the steps. They ran past strutters armed with splintered planks of wood, pieces of glass and broken tiles. Inside the cells the destruction continued.

From the steps, they stared down the levels. Black smoke billowed from the many small fires that were beginning to find each other; with no one putting them out, the flames were catching and taking hold. Great curtains of smoke hung in the roof. Spike had been hot before; now, as they looked around at the chaos, the whole place shimmered with heat haze.

Jimmy had been right. The rioters – Ant guessed two hundred, maybe more – had taken over the ground level and had started to climb to the first. Ant, Mattie, Amos, Jimmy and the Raaths led the way to level seven, their breathing becoming laboured. She was about to start opening cells there when they heard a buzzing noise. She pulled up short; everyone froze. As they watched, all ten cabins hummed, then the doors popped open.

Strutters poured out, relieved and terrified in equal measure. Each was quickly briefed about the need for weapons, and the smashing began again.

Cries from above. Level eight had also released its prisoners; they appeared at the railings above them. Jimmy Noon and others ran up to explain what was happening.

‘How did that happen?’ asked Mattie.

Ant looked up at the security cameras. ‘Someone’s watching,’ she said. ‘Who knows what their game is, but for the moment they’re helping.’

‘But if they’re all open, Dan and Gina will be out!’ cried Mattie.

‘No, I think they’re still shut. Look.’ Ant pointed down at the rioters. ‘They’re still looking up at us. If the lower floors were open, they’d be looking at them.’ She squeezed his hand. ‘Maybe it’s safer that way. They would have come out straight into the arms of that mob.’

Mattie swallowed but said nothing.

‘Where’s the fire brigade?’ asked Jimmy. ‘Where are the police? Army – anyone? How can it be like this? Prisoners versus prisoners!’

Jeffrey Blakely appeared on the stairs. ‘Because this is how they want it, young man, don’t you see? This is being allowed to happen.’

‘Well, that’s certainly how it feels,’ said Ant.

Jimmy Noon looked at her. ‘We need to escape then,’ he said. ‘If we can beat this lot, we should keep running. We need to get out of here.’

Ant absent-mindedly felt for the strap-key. And her heart stopped. It wasn’t there. She plunged her hand deep into her pocket. Nothing. She only had one pocket it would fit into, but she tried all of them anyway. Nothing.

‘Lost something?’ said Jimmy.

Ant shook her head, but Mattie had understood in an instant. His eyes wide, he held up four fingers. He mouthed ‘fourth level’, and she knew he was right. The case must have fallen out when the water cannon blasted them against cell 46.

They looked at each other, horrified. Ever since Ant had stolen Grey’s strap-key, it had been the focus of all their escape plans. There was no point in breaking out if everyone knew where they were. Why go on the run if the strap was beaming their location to anyone with a tracking device? They needed it back.

She felt Mattie’s hand in hers and knew they had to do this together. There wasn’t time to protest; there wasn’t time to find a ‘safer’ place for him – Ant doubted one even existed. So they pushed their way down the steps, past terrified families moving in the opposite direction. Those who noticed Ant and Mattie looked aghast.

‘Wrong way, kid!’ yelled one. ‘They’re coming this way – turn round!’

Between the sixth and the fifth they came face to face with one of Gina’s ‘lunch’ friends. She was brandishing three rudimentary spears: splintered lengths of plywood, a broken tile tied to one, splintered glass to the others.

‘Ant, it’s bad down there,’ she said. ‘You want me to take Mattie?’

Ant ignored her, pushing past and pulling her brother closer. She heard the woman call after them, ‘OK, take one of these!’ Ant turned just in time to catch one of the spears. She nodded her thanks, then, holding it high above her head, forced her way down.

Level four was emptying. They both crouched like sprinters on the landing, Mattie tucked in behind Ant, the spear gripped in her hand. She took as deep a breath as her smoky lungs allowed. Find the key, free Dan and Gina. That’s all. We can do it.

They scanned the floor, then shifted their gaze to the nearest fan, twenty metres away. Black smoke was drifting up from below then dispersing but Ant and Mattie weren’t watching. They only had eyes for a silhouetted object that lay hidden under its base. If you were walking past you’d have missed it, but viewed from ground level there was no mistaking the outline of Grey’s strap-key case.

They glanced at each other, then, with no time for caution, sprinted for the fan.

Mattie dived first. ‘Got it!’ he shouted.

He pulled his hand out, fingers wrapped tightly around the case. He checked its contents – the key was safe. It looked like nothing at all, but now, everything was possible again.

‘Kle!’ he said, and slapped it in Ant’s hand. She shoved it as deep as her pocket would allow.

Mattie crawled over to the railings and briefly peered down. ‘Looks like they’re fighting on level one now. There’s too many of them, Abi!’

She clasped his shoulder. ‘OK. We’ll be quick then,’ she said. ‘And invisible.’

Alone on the stairs, they ran down to level three. Cells 30 to 39 . . . They knew the cell layout by heart, knew everyone still locked inside; as they crawled to the corner of cell 30, Ant looked along towards the cabin they had lived in for the last two years. She gasped and grabbed her brother’s shoulder: Gina and Dan were hammering on the window, trying to attract their attention. They were shouting too, but their words were lost, muffled by the cell walls and obliterated altogether by the fighting below. It took Ant and Mattie a second to realize what they meant, then they spun round together.

The rioters had climbed to level three. One had scrambled over the railings and was in the process of helping two more. Through the railings, Ant saw that one of the new arrivals was grinning. She recognized Treves in an instant, and her blood ran cold.

‘Go!’ yelled Ant. They ran past the staring faces of their distressed neighbours; the panic-stricken banging was all around but they kept on running.

They closed on cell 33. Framed in the window, Dan and Gina were waving frantically, imploring them to put some distance between them and their pursuers.

‘Do it, Ant!’ yelled Mattie. ‘Swipe them out!’

Ant glanced round. Treves was now climbing over the railings. ‘OK!’ she said, and they headed for the cell door.

She checked Treves again. He had one hand pointing straight at her, the other cupped around his mouth. Above the din she heard him yell, ‘She’s here! The girl is here!’

A volley of well-aimed missiles fell from above – chunks of a cell wall by the look of them – and crashed into Treves.

As he stumbled, Ant swiped the pass through the entry pad of cell 33.