‘You can smell the cops before you can see them,’ he said. ‘Their aftershave.’ Here and there throughout the old quarries police he called the ‘catacops’ patrolled looking for trespassers. All entry to the catacombs was forbidden. And although the consequence of being caught was ordinarily only a small fine, the implications for us of being seen by the patrols were potentially fatal – for everyone. But the cat and mouse game the cataphiles played with the cops, he said, gave us one massive advantage. Although the people who explored that vast random city of the dead didn’t like strangers, they hated the police – and the system they thought they stood for – even more: no one who saw us would ask us who we were, or what we were doing. Anarchists, ravers, students, dreamers, lovers, potholers, cave divers, misfits, thieves and simply the downright curious – anyone and everyone could be found underground. Illegal bars hosting massive parties, Baaz told me, and even a fully functional cinema had been carved out in the inverted utopia that ran wild deep below the chic boulevards above. Graffiti, sculptures and elaborate shrines marked the waypoints of a world that I’d imagined I could navigate but that would have swallowed me without trace. I considered this, too: my father’s route map might not have led me out of the catacombs, but it had led me to Baaz – which, right then, seemed like the next best thing.

Several times a light at the end of a cross tunnel saw me raise the Glock in expectation of trouble. But each time Baaz waved my hand down.

‘Carbide,’ he explained. ‘They’re explorers. The cops use LEDs like yours. It’s cool.’

The challenge of getting us to the ancient necropolis of Montparnasse gripped him obsessively. He didn’t ask me about myself; I asked nothing more about him. The fact that our clothes were soaked and steaming, that we were filthy and scuffed and only alive by the thinnest of margins, weren’t things he was ready to talk about, now or maybe ever. If he was in shock, he was still functioning; if he wasn’t in shock, he was, frankly, a freak. I was in shock. But Baaz, he just turned and turned again, until the level of the floor started first to ascend and then climb sharply. We were getting nearer to the surface. We branched away from the main tunnel, clambered through an antechamber furnished with a wax-smeared stone table, and then made a hunched thirty-metre walk to what looked like a dead end.

In fact, we’d reached a low arch in the tunnel wall. He killed the light. I tensed. We stood next to each other in deep, impenetrable darkness.

‘What is it?’ I whispered, pushing the pistol up and out with both hands into the pitch black. ‘Where?’

‘Forward,’ he replied, voice tense with expectation. ‘Crouch. Slowly.’