First a little tear appeared… then a bigger one... and then suddenly the smoothed-out silver below Lucia was shredding away, turning into little glittering cloudlets, then vanishing.

Revealing an amazing sight far below them as the Tracboat sped along, still inside her mirror-walled circle.

It was like a huge frozen sea, only deep gold in colour. Scattered about on the sides of the waves, along winding pathways, were thousands and thousands of what looked like tents – all the colours of the rainbow: green, red, purple and yellow. Lucia was still so high up they looked like toys.

Some were small, bell shaped, with bulgy round sides. Others were like houses, with doors and windows. But all had flags flying from them, fluttering and twisting on the little masts that held them.

“Wow!” said Dot.

“Superbe!” said Fromage, gazing down with her.

“Hic!” went Wiz.

Walpurgis turned round from his seat at the Tracmapper and waved his arm in a very royal manner.

“Welcome to the Valley of Sleep!” he said. “Decline down, please Lucia!”

Very smoothly the Tracboat tipped her bow down. As she did so, the mirror wall started to fold back from around her, rolling towards its centre point on either side.

“What was that for – that wall?” asked Dot.

“It was what’s called an Expediter” said Walpurgis. “One of our little tricks – Hombellyton dreamed it up, and we can sing it into life any time we want, like we just did. Makes us go faster – the Valley of Sleep is a long way into the Tzone, you see.”

They were getting closer to the strange frozen golden sea now.

“Easing to net-land, Lucia, please! Aiming CERULEAN!” said Walpurgis.

“I do hate this place” grumbled Eldenbeam. “It’s so boring!”

“ ‘Ow do you mean, bor-ing?” said Fromage, rolling his eyes at Dot. “Looks good to me!”

“One minute to net-land, everyone!” called Walpurgis. The other TricTrucTrackers were, as usual totally relaxed: Carmeramalita was reading a book called ‘Tracmapping: New Ideas in Net-space’, Hombellyton was asleep (so was Wiz!), and Katzilow was humming to himself. Eldenbeam let out a big sigh.

Dot thought she’d better stop him before he started another row. She knew he liked telling you stuff, so –

“What is the Valley of Sleep, please, Mr Eldenbeam?” she asked, in her best polite voice. She needed to know, too!

“Well – of course Wally should have told you this already” said Eldenbeam (luckily Walpurgis didn’t hear him!) “But it’s where Wisps are centralized – in a shutdown state, so that’s why it’s called the Valley of Sleep.”

“Wisps…?” asked Dot, more confused than ever.

“Oh, Wisps” replied Eldenbeam. “Well, Wisps are shadows of lost or abandoned devices. They’re made up of all the things they did before they were lost. So, if it’s a keyboard we’re talking about, it’s all the keystrokes it ever made, in one bundle. Or if it’s a screen, it’s all the pictures and documents it ever showed. If it’s a mouse, it’s all the clicks and scrolls. In computer programme form of course – but each Wisp looks like the device it comes from. You’ll see!”

“Thirty seconds to net-land!” called Walpurgis.

Now they were closer, Dot could see how big many of the tents she’d seen from high up really were – like houses, but still tents. Lucia was about 100 metres above them now, coming down in a shallow, curving dive.

“What are those tent things for?” she asked, pointing.

“They’re Wisp colonies” said Eldenbeam. “Each device family has one. Those flags tell us which is which. Lucia is now trying to get us near to Colony Cerulean – where all the mice like your Mr Mouse are Wisp-stored. Then we can start our close-in search. We’ll have some work to do, I can tell you!”

The Tracboat was now just 10 metres up above the frozen golden sea. She flew smoothly, avoiding the trees that dotted pathways between the Wisp colony tents very neatly, though she was still travelling at speed.

Now they were down, Dot could see how big the Valley of Sleep was – or rather, she couldn’t: it stretched away on all sides, the rolling wave-like hills covered in tents and trees.

“Five seconds!” called Walpurgis.

With a sliding hiss, Lucia let herself fall onto a broad pathway across the wave-like ground. As she touched, Dot could tell how fast they’d all been travelling. Tent after tent sped past in a blur of different shapes and sizes and colours. And flags.

Slowly Lucia came to a stop, right next to a giant tent made of a dazzling blue material, edged in green and black and with a flag flapping from the top of it.

It was one of the tents like a house, square and with windows on the sides. They weren’t real though – just painted on. Its sides – stretching up as high as her home in Barking Avenue – fluttered slightly too, though Dot couldn’t feel any wind.

With a click and a little “Dringg!” the safety sets withdrew. Walpurgis stood up and stretched his furry arms, opening his funny flat beak wide.

Wiz woke up. “Hic HIC!” he went. “Rats and double rats! If you must stay inside me Buzby will you keep still!”

“Here we are!” he said, beaming at everyone on board. “Colony Cerulean!”