‘Uh?’ he said.

‘You all right?’ said Yo-less.

‘Let’s get a drink, at least,’ said Kirsty, shoving the trolley firmly towards the town centre.

And then she stopped.

Johnny hadn’t often seen her shocked. Kirsty normally dealt with the terrible and the unexpected by getting angry with it. But now she stopped, and went pale.

‘Oh, no …’ she said.

The road from the old church led down the hill towards traffic lights at the bottom.

An overloaded shopping trolley, with a boy and a girl clinging to it, was hurtling down the other road.

As they watched, it heeled over like a yacht tacking against the wind, turned a full ninety degrees, and plunged into the car park of the Neil Armstrong Shopping Mall.

A long black car followed it.

He’d forgotten all about the car. Maybe there were secret societies. Maybe there were men in black in long black cars who said things like, ‘The truth is out there’ and came and found you if you got your hand trapped in the occult.

Johnny could see a map in his head. But it was a map of time.

They’d moved in time at his house. But Yo-less was right, you probably could move in time like a train on a track, so you flipped over onto another track just a little bit further along. You moved in space, really.

And he’d done it again, when he thought they were going to die at the traffic lights. And the black car had vanished … because it didn’t exist in this time. He definitely hadn’t seen it when he’d looked behind him.

They’d come back to a time when it existed.

The car pulled to a halt outside the mall.

A feeling of absolute certainty stole over Johnny. He knew the answer. Later on, with any luck, he’d find out what the question was, but right now he was sure of the answer.

Forget about secret societies. Forget about time police. Policemen had to have nice logical minds, and to deal with time you needed a mind like Mrs Tachyon.

But there was someone else who’d know where they’d be today, wasn’t there …

Because … supposing we didn’t go back? Supposing … maybe we went back and did things wrong?

He started to run.

Johnny dodged across the road. A car hooted at him.

Across in the car park, a man in black, with black sunglasses and a peaked black hat, got out of the car and hurried into the mall.

Johnny leapt over the low wall into the car park and weaved between shoppers and their trolleys …

… and panted to a halt in front of the car.

It had stopped right in front of the entrance, where no one was ever allowed to park.

In the bright sunlight it looked even blacker than Johnny remembered. Its engine ticked occasionally as it cooled down. On the hood was a silver ornament.

It looked very much like a hamburger.