The three of them nodded as the bulb above them flickered and fizzed ever so slightly.

‘In the same way, it’s impossible to step through into the past without creatinga ripple. But the problem is the ripple spreads and grows from the point at which someonesteps in. From that we get a tidal wave that increases in size and destroys everything in itsway to replace it with a new world… a universe that might havebeen.’

Liam shook his head. ‘Not sure I understand.’

‘I get it,’ said Sal. ‘If you change the past a little, you’ll changethe present a lot.’

Foster nodded. ‘That’s exactly right, Sal.’

The light dimmed for a moment, then winked on and off. Foster looked up at it, irritated.‘The bulb’s worked loose again.’

He stood and, carefully covering his hands with the sleeve of his jumper, twisted the bulb.The flickering stopped.

‘We need to rewire this place… but there never seems to be enoughtime.’

Maddy looked around. ‘Where are we? It looks like some skanky old railwayarch.’

Foster smiled. ‘That’s pretty much what it is. It’s actually a-’

The light dimmed and flickered once more and his eyes suddenly widened.

‘Oh no.’

The others looked up at his face, all of a sudden a shade paler.

‘What’s up?’ asked Maddy.

‘It’s here…’ he whispered.

‘A shift?’ asked Liam.

‘No — ’ he shook his head — ‘worse.’

CHAPTER 7

2001, New York

Foster’s eyes remained on the fizzing and flickering light bulb.‘It’s draining the energy. I thought it was the damned light bulb on the fritz.Stupid of me,’ he hissed.

‘What’s draining the energy?’ asked Maddy.

The strained tone in Foster’s lowered voice unsettled the others.

‘I thought the thing had gone.’