It was really strange, rising up through the blue air inside Colony Cerulean, surrounded on all sides by the Wisps of Cerulean family mice.

It was sort of like being under the sea, except you weren’t wet and didn’t have to wear goggles. And of course they were all riding in a little seat – Walpurgis’ “courtesy carrier” – which had folded out of the TricTrucTracker’s backpack.

As they rose up, with Walpurgis lifting and moving them all forward by making moves with his arms a bit like the breast stroke in swimming, the Wisps gently moved out of the way, just as they’d done when Fromage tried to touch them.

“Hum DEE da dee da” went Walpurgis into his little MiniTrac. It responded with a “Plink!” noise.

“What does that – HIC! – what does that mean?” asked Wizzie, curious as ever despite having a bee-like Buzby still fluttering about inside him.

“It’s just acknowledging my personal lock-on to Hyphenmarc 650R” said Walpurgis, twisting round to smile at them. “What we all did before was a group capture. This one’s just for us.”

“Plink-DINK!” went the MiniTrac. “And telling me to turn left now!” said Walpurgis. “Looks like we have a trace around 72 cyber-metres left, so let’s go there! It’s some way off though - it’ll take us a while.”

He made a kind of paddling motion with his left arm, and off they went to the side, climbing still further as they did so.

Still there seemed no end of Colony Cerulean – everywhere they looked the Wisps floated, always politely moving aside to let them past, in their strange, fish-like way.

“ ’Ow big ees thees place then?” asked Fromage.

“Oh, well, let’s see” said Walpurgis. “Ermmm – well, take your big football stadium in Paris… ”

“Ze Stade de France?” said Fromage. “Magnifique! Vairy many meese live in it – a good place for music too! I saw Minnie and the Mice there once! Cool evenings!”

“Mmm, yes” said Walpurgis, obviously a bit startled by this bulletin from the world of rodent rock. “Well, this Colony is larger than that. It’s one of the biggest storeplaces in any Tzone, in fact!”

Just our luck, thought Dot.

“Plink-DINK DINK! went the MiniTrac, as if it was ticking Walpurgis off.

“Oops, too far right” said the TricTrucTracker. “Adjusting!” They banked a bit to the right.

“So… is that what Tzones are, then?” asked Dot. “Kind of storage places…?”

“Yes, I suppose so really” said Walpurgis. “There’s Tzone11 – that’s where all past e-mails are held…Tzone29 – that’s got all searches on the Internet… and Tzone53, which is the home of computer games, past and present. And that’s just a few of them. But 66 is the place to start finding lost and damaged devices – because the Wisps can tell us where they are. Look!”

He pointed to a Wisp right next to them.

“What?” asked Dot, feeling puzzled again. She hadn’t seen a thing!

“Oh – you have to be quick. Ah! There! Look again!”

This time Dot did see it – a tiny pin-prick of orange light inside a Wisp right next to them. Gone literally in a flash.

“What does that mean?” she asked.

“It’s telling us someone’s just used that mouse on-line somewhere” said Walpurgis. “The electronic signal goes straight to its Wisp, and get stored. The thing is, it doesn’t happen very often with lost or damaged ones, as you’d expect. But that click – they’re orange, scrolls are purple – gives a precise place where that particular mouse is right now. Only if the PC or laptop it’s attached to is on-line, of course – otherwise the signal can’t get into cyber-space. Ah!”

The MiniTrac had started to glow a faint green colour.

“WHAT a stroke of luck!” said Walpurgis excitedly. “We could be closing on your Mr Mouse!”

At this point, without Walpurgis doing anything, they dipped down and up and shot off further to the right.

“Wa-hey!” said Wiz. “Steady!”

“It’s OK” said the TricTrucTracker chief (a little breathlessly!) “When we get close, MiniTrac takes control!”

With the Wisps scattering on either side of them, they zoomed along – and then suddenly burst out from the thousands of Ceruleans into a clear open space with a single Wisp hovering in the middle, outlined in a kind greeny-golden light.

Well, a clear space if it weren’t for a crowd of TricTrucTrackers – the whole crew, in fact, Katzilow, Hombellyton, Eldenbeam, and of course Carmeramalita.

And equally of course, a big argument was going on.

“It was me that search-found first! I can prove it!” (Katzilow.)

“Nonsense! Look at the time-data on my MiniTrac!” (Eldenbeam.)

“Well I got the Clear-Zone started!” (Hombellyton.)

“Does it matter, boys? Chill!” (Carmeramalita. Natch!)

Walpurgis shot into the centre of his argy-bargy crew and rocked to a sudden halt, making Dot squeeze Wiz tight and clutch at Walpurgis’ backpack straps so they didn’t fall out of the courtesy carrier. Fromage gave a squeak, even though he was safe under the shoulder of her T-shirt.

“ENOUGH!” Walpurgis roared. “The main thing is, we've found Mr Mouse’s Wisp. And that’s all that matters. If we keep - ”

“Hic! Neep-Barp!” went Wiz. “Neep-Barp! Neep-Barp!”

All the TricTrucTrackers stopped arguing and looked at him, open mouthed.

Wiz swallowed hard and the funny sounds stopped. “WHAT is that dingbat Buzby doing inside me now!” he growled. “First hiccups, and now silly noises! I’m fed up with this!”

“Not so fed up as we all could be very soon!” said Walpurgis, suddenly looking very worried.

“That’s a Buzby call sign – if a Zonemaster is nearby.”

He looked round at them all.

“It means Nascarbalone Trinth is after us!”