Entering the fog was like having a thick grey blanket thrown over them. Jackie tensed, clenching her fists, holding her breath. The light from the headlamps bounced back, as if from a mirror, dazzling them. Instinctively, Joe braked.

'I'm not happy about this,' he said.

'Just keep going,' said Jackie. 'It's a freak fog bank, that's all. Cold and warm air colliding or something. Just take it slowly and we'll be through it in a minute.'

Joe nodded, and for the next few minutes the car crept forward at little more than twenty miles an hour. All the while, the fog rushed and swirled towards them like something furious and alive. Mesmerised and unnerved, Jackie forced herself to blink, told herself she couldn't really see shapes trying to form from the muscular grey vapour. Her brain was simply trying to make sense of the constantly shifting shapelessness of it. It was a natural human reaction — like seeing faces in clouds, or looking for patterns in the chaos of nature.

It wasn't only her sight that was affected, though. She fancied she could smell the fog, like thick, sour soup, and she was equally certain that it was playing havoc with her hearing, filling her ears like cotton wool, blurring the music into a mushy buzz, reducing the throaty growl of the engine to flat, bland static. She opened her mouth wide, trying to yawn, hoping her ears might pop. And then she did yawn, and was dismayed to find that it made no difference. She felt a stab of anxiety. Maybe the fog was toxic; maybe it was affecting them physically, like nerve gas or something. She wondered whether she should say something to Joe, but she was almost afraid to speak, in case she found out that she could no longer string two words together.

And then suddenly, without warning, they were through.

It happened in a blink. One second they were crawling forward through impenetrable greyness, and the next the road ahead was clear, and the moon fat and bright again, spilling its light onto the land.