All they had were those little green glow sticks, those and their work-wear. Everything else had been lost. Her bag, her clothes, left back at Leicester Square, had to be nothing but ash by now.

She had no real idea of where she was, either, only that there had been emergency exit signs and that they’d seemed like the only hope of escape. Going back had been out of the question. Going on had been just as unlikely: she’d been on her last legs, and she was used to running.

She hadn’t had to persuade the others to follow her. They’d just piled in behind her, fewer than she’d expected, and blundered around in the dark until someone had found the way up.

It had been almost too late: the naked metal grille they’d had to pass, which led back out to the tunnels, had been glowing cherry red, and the heat had been almost too great to bear.

She couldn’t remember if there’d been more than five of them at that point. Perhaps they’d lost someone else between then and now, too frightened, too tired to carry on.

There were five. And shortly there’d be more.

She moved to the back of the group, holding her glow stick high. There was a little door in the wall at the end of the short corridor where they were huddling, and just as she reached it, it opened at her.

She shrieked, and that brought a cry of shock from the other side. A bright white light struck her full in the face, and she raised a hand to shield her eyes.

‘Point it somewhere else, you fucking idiot.’

‘Sorry.’

The torches turned their aim toward the ground: the damage was done, though. Night sight ruined, Mary couldn’t see anything.

‘How many of you are there?’

‘Two. There’s two of us.’ The voice that spoke seemed very proper, very English, despite the hoarseness. ‘How many are you?’

‘Five.’ There’d been twenty of them when they’d started. How could there be only five left? ‘What’s happening? Why is everything on fucking fire?’

‘Do I look like I know?’

She couldn’t tell what he looked like, but someone with that accent ought to know.

‘Well, do you?’

A voice behind the first man spoke. ‘Miss? Please move out of the way. We would like to come in.’

She shuffled to one side, and two dark shapes edged past. They headed towards the remains of the cleaning crew, leaving her with the door. Noises – bad noises – echoed from below, grinding and groaning and booming, as if a monster was loose in the tunnels.

Perhaps there was a monster loose in the tunnels. It made as much sense as anything.