It was a shock to find it so close, though. The kids had learnt to avoid the area between the Tower and the cathedral. It was part of the no-go zone, the old financial district. Weird things happened there. Like what had happened to Leo. The streets this way were far too dangerous. Some time ago a couple of groups had set off to explore in that direction, and had never come back. Jordan Hordern forbade anyone else from heading there. Nowadays, if the kids at the Tower wanted to go further than the surrounding area, they headed east, or south, across Tower Bridge. The fire hadn’t made it this far along the river and there were rich pickings in the houses and shops over the water.

‘What was his name?’ said DogNut who had been following his own train of thought.

‘Who?’ said Courtney.

‘The nutjob who wanted to go to St Paul’s? Crazy freak who made that stupid flag and was always spouting, like, religious stuff.’

‘Matt.’

‘That’s it, Mad Matt. Wonder if he ever made it there?’

‘I hope he drowned,’ said Courtney flatly.

When they’d escaped from the fire on the tourist boat, Matt had gone crazy and tried to change their course downriver to the cathedral. It was his fault that the boat had crashed and sunk and Aleisha had been sucked into the river. Matt had last been seen floating away on a piece of wreckage with his followers.

Courtney wondered if he’d made it, if he’d been living in St Paul’s all this time. So near, and yet a million miles away. It was weird to think of all the other kids who must be out there, in their own small groups dotted around London, trying to survive, only knowing their own patch.

A thought struck Courtney.

‘We’re doing a good thing,’ she said. ‘Isn’t it?’

‘Is it?’ said DogNut. ‘I don’t think I ever done nothing good before.’

‘Exploring,’ said Courtney. ‘Seeing what’s out there. Meeting other kids. Pulling everything together.’

‘You jumping ahead of yourself,’ said DogNut. ‘We ain’t met no one yet.’

‘But we will.’

‘Look at that,’ said Jessica, from her bench directly behind them.

DogNut and Courtney looked round. They had reached the edge of the fire damage. The buildings all along the south side of the river were blackened and broken – it was a desolate wasteland. With no emergency services to put the blaze out it had raged for days, eating away at the city until rain and a change in the wind had finally halted it. A haze of smoke had hung over London for months after it had happened but now the skies were clear.

As the kids stared in fascination at the ruins they lost concentration and the boat was quickly out of control and turning in the water. It took some shouting and cursing until they finally got it straightened up and moving smoothly again, but they still couldn’t help looking as they slid past the seemingly endless devastation. It brought it home to them all just how dangerous their mission was. Just how much London had changed.

As if to ram the point home, two dead bodies floated past. A little girl who must have been no older than five or six, her body puffy and bloated, her eyes eaten by fish, and a middle-aged man, his greenish skin covered in lumps and boils and swellings so that he looked like nothing so much as a giant dead toad.

The boat fell silent, all their efforts now focused on rowing, which was much more tiring than they’d expected, despite all their practice. It had felt easy at first, but they were becoming all too aware of just how big the river was, how heavy the boat was and how far it was to Lambeth Bridge. The bench seemed to dig into DogNut’s backside so that he could feel every knot and ridge of grain in the hard wood. His back and arms ached; his hands felt raw.

They’d come to Waterloo, where there was a big bend in the river. They realized they would have to fight the fierce current that wanted to pull them to the north bank. Marco and Felix, who had been muttering at each other for the whole journey, raised their voices.

‘You got to row harder,’ Felix snapped.

‘It’s you who ain’t rowing hard,’ said Marco. ‘The boat’s, like, twisting round. You got to dig into the water.’

‘What with? A spade?’

‘No, with your oar, stupid.’

‘I am digging in with my oar, you spaz. What do you think I’m doing?’

‘Don’t call me a spaz, you spaz, you’re gonna get us drowned.’

‘Will you two shut up!’ DogNut shouted. ‘And concentrate on not hitting the bridge. If we don’t hold our line, we’ll smash up against it.’

‘You know you shouldn’t use that word,’ said Olivia to Marco and Felix.

‘What word?’ said Marco, fighting for breath.

‘Spaz. It’s a bad word. Paul hit someone once who said it.’

‘Who’s Paul?’

‘He’s my brother. He’s the one we’re going to find.’

‘Right.’

‘We had a cousin who was disabled. He was always getting bullied and Paul was always sticking up for him.’

‘He sounds like a nice guy, your brother,’ said Marco kindly.

‘He sounds like a dick,’ Felix murmured under his breath. Marco tried not to laugh. Luckily Olivia hadn’t heard him.

‘He’s brilliant,’ said Olivia. ‘When my mum and dad died he looked after me.’

‘We’ll find him,’ said Marco.

‘The dick,’ Felix added, slightly too loudly, and Marco snorted.

Olivia was about to say something else when Finn spoke for the first time.

Two words.

‘Big Ben.’

‘Nearly there,’ DogNut gasped. ‘Lambeth Bridge is right after the Houses of Parliament.’

But the rising tide was starting to lose its energy and no matter how hard they pulled on the oars it was almost as if they weren’t moving at all. It got harder still as they passed under Westminster Bridge. The water here foamed and churned as it bunched up by the stonework. If they weren’t careful they’d be swept on to one of the supports. Nobody said a word as they strained to keep the boat straight.

At last, nearly an hour after setting off from the Tower, they dragged the boat clear of the swirling, roaring water and emerged into the light at the other side of the bridge.

DogNut felt a surge of relief, but noise and movement made him look up and he saw a row of people craning over to peer at them from the terrace that ran along the back of the Houses of Parliament, overlooking the river.

He had a moment of panic, but was relieved to see that they were all kids. They must have spotted the rowing boat and come out to see what was happening. There wasn’t a sick adult in sight. It gave him hope and renewed strength. He urged the others on. They had planned to row across to the south bank and land at Lambeth pier, but the kids along the embankment were shouting at them and gesturing towards their side of the river.

DogNut looked at Finn. There were still strong currents in the water and they were struggling to control the boat.

‘Maybe we should go closer and see what they want.’

Finn said nothing, just gave a brief nod.

‘Over to you,’ said DogNut. ‘Guide us in.’

Finn nodded again. ‘There’s a set of stairs leading up from the water,’ he said. ‘At the other end of the buildings. Might be a safe landing place.’

‘We could give it a shot.’

Whatever happened, they couldn’t stop rowing. If they did, the current would take over and pull the boat sideways along the river past where they wanted to land. So they kept close to the edge and Finn directed them towards the steps. They could hear the kids shouting down at them from the terrace.

‘Where are you from?’

‘Where did you get the boat?’

‘Who are you?’

He couldn’t make out the rest – they were talking over each other. And DogNut had a question of his own.

‘Are those stairs over there safe?’ he yelled.

‘As far as we know.’

‘They should be.’

‘Haven’t you never used them?’

‘We don’t have any boats.’

‘What do you reckon?’ DogNut asked Finn. ‘Shall we risk it?’