"I saw the back of my own head!" whispered Johnny. "My actual own back of my own head! Without mirrors or anything! No-one's ever done that since the Spanish Inquisition! How can you be so calm about this?"

"I'm just acting calm," said Kirsty. "This is even worse wallpaper, isn't it? Looks like an Indian restaurant."

She opened the front door, and slammed it again.

"You know I said that if you started getting too interested in mysterious occult things these men in black cars turn up?"

"Yes? Well?"

"Look through the letterbox, will you?"

Johnny levered it open with a finger.

There was a car pulling up outside. It was black.

Utterly. Black. Black tires, black wheels, black headlights. Even the windows were darker than a pair of Mafia sunglasses. Here and there were bits of chrome, but they only made the blackness blacker by comparison.

It stopped. Johnny could just make out the shadow of the driver behind the tinted glass.

"S ... just ... coincidence," he said.

"Your grandad often gets visitors like this, does he?" Kasandra demanded.

"Well ... " He didn't. Someone came round on Thursday to collect his football pools coupon and that was about it. Grandad was not one for the social whirl.

The car door opened. A man got out. He was wearing a black chauffeur's uniform. The car door shut. It shut with the kind of final, heavy thonk that only the most expensive car doors can achieve, because they are lined with money.

Johnny let go of the letterbox and jumped back.

A few seconds later, someone banged heavily on the door.

Run!" whispered Kasandra

"Where?"

"The back door? Come on!"

"We haven't done anything wrong!"

"How do you know?"

Kasandra opened the back door and humied down the path and into the garage, dragging Johnny behind her. The trolley was still in the middle of the floor.

"Get ready to open the big doors and don't stop for anything!"

"Why?"

"Open the doors now!"

Johnny opened them, because practically anything was better than arguing with Kirsty.

The little garage area was empty, except for someone washing their car.

Johnny was nearly knocked aside as the trolley rattled out, with Kasandra pushing determinedly on the handle. It rattled across the concrete and lurched uncertainly into the alleyway that led to the next road.

"Didn't you see that program about the flying saucer that crashed and these mysterious men turned up and hushed it all up?" said Kasandra.

No.

"Well, did you even hear about the flying saucer crashing?"

"No"

"See?"

"All right, but in that case how come there was a TV program about it, then?"

A car edged around the corner into the road.

"I can't waste time answering silly questions," said Kasandra. "Come on."

She shoved the trolley as hard as she could. It rolled down the sloping pavement, the squeaky wheel bouncing and juddering over the slabs.

The car turned the corner very slowly, as though driven by someone who didn't know the area very well.

Johnny caught up with Kir-Kasandra and clung to the handle because the trolley was rocking all over the pavement.

The trolley, under its heavy load, began to pick up speed.

"Try to hold it back!"

"I'm trying! Are you?"

Johnny risked a look behind. The car seemed to be catching up.

He jumped onto the trolley.

"What are you playing at?" said Kirsty, who was far too worried to remember any new names now.

"Come on!"

He grabbed her hand and pulled her up on the other side of the cart. Now she was no longer holding the handle, it surged forward.

"Do you think this is really a time machine?" he said, as the rushing wind made the bags flutter.

"It must be!"

"D'you see that film where the car travelled in time when it went at eighty-eight miles an hour?"

They looked down. The wheels were screaming. Smoke was coming out of the axles. They looked up the hill. The car was catching them up. They looked down the hill. There were the traffic lights. The Blackbury by-pass was a solid wall of thundering traffic.

Then they looked up into each other's frightened faces.

"The lights are red! The lights are red! I don't want to die!" said Kirsty. "I haven't even been to university!"

One hundred metres ahead, sixteen-wheeled lorriies barrelled onwards, taking a million English razor blades from Sheffield to Italy and, coming the other way, a million Italian razor blades from Rome to England.

The trolley was, without a shadow of a doubt, going to smash right into the middle of them.

The air flickered.

And there were no lorries, or, rather, there were lorries, snorting and hissing and waiting at the lights. The lights ahead of Johnny were green.

The trolley rolled through, wheels screaming. Johnny looked up into the puzzled faces of the drivers.

Then he risked a look behind.

The black car had vanished.

There were no other turnings off the hill. Wherever it had gone, it hadn't got there by any means known to normal cars.

He met Kristy's eyes.

"Where did it go?" she said. "And what happened with the lights? Did we travel in time again?"

"You're wearing your mac!" said Johnny. "You were wearing your old coat but now you're wearing your mac! Something's changed!"

She looked down, and then back up at him.

Beside the crossroads was the Neil Armstrong Shopping Mall. Johnny pointed to it.

"We can make this go into the car park!" he shouted.

The big black Bentley jerked to a halt at the side of the road. "They just vanished!" said Hickson, staring over the top of the wheel. "That wasn't ... this time travel stuff, was it? I mean, they just vanished!"

"I think they went from one now to another now," said Sir John.

"Is that ... like ... these trousers you were going on about, sir?"

"I suppose you could say they went from one knee to the other. One 1996 to another 1996."

Hickson turned around in his seat.

"Are you serious, sir? I saw this scientist on TV... you know, the one in the wheelchair ... and there was all this stuff about other universes all crammed in, and-"

"He'd know the proper way of talking about it," said Sir John. "For the rest of us, it's easier to think about trousers."

"What shall we do now, sir?"

"Oh, I think we wait until they come back to our now."

"How longs that going to be?"

"About two seconds, I think ... "

In the shopping mall, a joke was going wrong.

"Make me ... er," said Bigmac, "make me one with pickle and onion rings and fries."

"Make me one with extra salad and fries, please," said Yoless.

Wobbler took a long look at the girl in the cardboard hat.

"Make me one with everything," he said. "Because ... I'm going to become a Muslim!"

Bigmac and Yoless exchanged glances.

"Buddhist," said Yoless, patiently. "It's Buddhist! Make me one with everything because I'm going to become a Buddhist! It's Buddhists that want to be one with everything. Singing 'om' and all that. You mucked it up! You were practicing all the way down here and you still mucked it up!"

"Buddhists wouldn't have the burger," said the girl. "They'd have the jumbo Beanburger. Or just fries and a salad."

They stared at her.

"Vegetarianism," said the girl. "I may have to wear a paper hat but I haven't got a cardboard brain, thank you." She glared at Wobbler. "You want a bun with everything. You want fries with that?"

"Er ... yes."

"There you go. Have a day."

The boys took their burgers and wandered back out into the mall.

"We do this every Saturday," said Bigmac.

"Yes," said Wobbler.

"And every Saturday we work out a joke."

"Yes."

"And you always mess up the punch line."

"Well ... it's something to do."

And there wasn't much else to do at the mall. Sometimes there were displays and things. At Christmas there'd been a nice tableau of reindeers and Dolls of Many Countries that really moved (jerkily) to music, but Bigmac had found out where the controls were and speeded up everything four times, and a Norwegian's head had gone through the window of the cookie shop on the second floor.

All there was today in the way of entertainment were the people selling plastic window frames and someone else trying to get people to try a new artificial baked potato mix.

The boys sat down by the ornamental pond, and watched out for the security guards. You could always tell where Bigmac was in the mall by watching the flow of the security guards, several of whom had been hit by bits of disintegrating Scandinavian and bore a grudge. As far as anyone knew, Bigmac had never been guilty of anything other than the occasional confused approach to the ownership of other people's cars, but he had an amazing way of looking as though he was thinking about committing some rather daft crime, probably with a can of spray paint. His camouflage jacket didn't help. It might have worked in a jungle, but it tended to stand out when the background was the Olde Card and Cookie Shoppe.

"Old Johnny may be a bit of a nerd but it's always interesting when he's around," said Wobbler. "Stuff happens."

"Yeah, but he hangs around with Kimberly or Kirsty or whoever she is today and she gives me the creeps," said Yoless. "She's weird. She always looks at me as if I haven't answered a question properly."

"Her brother told me everyone expects her to go to university next year," said Bigmac.

Yoless shrugged. "You don't have to be dumb to be weird," he said. "If you're brainy you can be even weirder. It's all that intelligence looking for something to do. That's what I think."

"Well, Johnny's weird," said Bigmac. "Well, he is. It's amazing the stuff that goes on in his head. Maybe he is a bit mental."

"It's amazing the stuff that goes on outside his head," said Wobbler. "He's just-"

There was a crash somewhere in the mall, and people started to shout.