‘Thanks.’ He flicked it on. If you need someone on side, show them you have faith in them. It’s reassuring to be trusted. ‘Cool. You don’t need it for your …’ he tailed off and pointed to the M4.

‘For the rifle? No. You know your way around. So you’re going to need it. Because you’re going first.’ He smiled. ‘Besides,’ I added, ‘if anyone shoots at us, they’ll aim at the torch.’

‘What?’

‘OK, let’s go.’ We shuffled into the main tunnel. I slung the M4 over my shoulder and drew the Glock.

‘No, but seriously.’

‘Yes, but seriously. Let’s go.’

‘Go fucking where?’

‘Montrouge,’ I said. ‘The cemetery.’

He turned around to face me again, staring in disbelief. ‘No way.’

‘Listen.’ My voice was stressed, too forceful. He recoiled. ‘Listen, Baaz,’ I tried again, softening. ‘I need to get out of the city, out of France. I can’t explain more than that. If you can get me west of Place d’Italie, I can get myself out. I’ll find the way.’

‘How?’ he asked, incredulous.

‘I cut waypoints down here when I was a kid. I know what I’m doing.’

‘No,’ he said, ‘you don’t. No offence, but that must have been, like, years ago?’ I shrugged. ‘Montrouge is messed up,’ he added excitedly. ‘A hundred metres of tunnel came down before Christmas. What didn’t collapse, flooded.’

‘There’s no way?’ I asked, thinking, There’s always a way.

He shook his head emphatically.

‘It can’t be done. Trying to get out there would be suicide.’

‘Staying down here is suicide. As soon as those two dead guys fail to check in with the rest of their team, a tsunami of shite is going to flood these tunnels.’ I looked around at the passage walls, pointlessly. ‘Fuck!’ I could feel my temper fraying in exasperation. I breathed deeply and composed myself. ‘Can they seal the catacombs? I mean, completely cut them off?’

‘No,’ Baaz replied. ‘Impossible. For a start there could be dozens of cataphiles down here right now, maybe even hundreds.’

‘Who?’

‘You know, people who come exploring at the weekends, like me. Tourists, students.’ He paused for a moment. ‘All sorts of weirdos.’

‘So what?’

‘So, if you sealed the entrances, we’d die. There are always people down here, so the cops always have to leave exits open. They’d be done for murder otherwise.’

I decided not to press the point that the people after me – after us – weren’t overly concerned about their rap sheet.

‘OK. If not Montrouge, where? We can’t use an exit the police know about.’ He thought for a moment, twitching the fingers of his left hand as if tapping an invisible keyboard. ‘Baaz,’ I urged him, ‘we really need to move.’

I started to pace up and down, hanging on to the coat-tails of my temper.