And everything was dark ahead of the engine. Really dark. The curve of the tunnel meant that you could only ever see one entrance at a time. In fact, there was a point, right in the middle of the tunnel’s arc, where you couldn’t see any light at all; but he didn’t care to think of that right now. His breath billowed up in front of his face like steam, partially obscuring his view of the sunlit opening ahead each time he exhaled.

He should have been thinking about how they were going to get to the maintenance yard forty kilometres away without too much damage or time loss: he should have been thinking like an engineer. But he wasn’t. All he could hear, echoing in his head as though his skull were a tunnel, were the words, the living rock, the living rock.

He hadn’t needed the torch for the first few yards, the walls being lit by the cab interior, but by the time he drew level with the first car, Joshua had to use it, picking his way along the track trying not to pratfall over the sleepers half-buried in gravel. The arch of sunlight was clear ahead, its illumination extending barely a few feet into the dark, and already he was starting to regret he hadn’t insisted that Barney come with him. He touched the walkie-talkie hanging on his hip, annoyed that it hadn’t crackled into life. Clearly his two crew companions were treating this like a break instead of a breakdown. He was tempted to press ‘talk’ and shout horse’s ass at them as he passed the second car just to remind them he was there, but realized grimly that it wasn’t irritation making him keen to summon them, but apprehension. His hand left the radio, unclipped the ear flaps on his cap and let them fall. Joshua Tennent was suddenly very cold.

It wasn’t so much a noise he heard, more the feeling of a noise. That is, he sensed there was something scraping in the rock above him. Not scraping on the surface, like a bat or a chipmunk, but scraping inside the rock as if the stone itself was shifting, turning in its sleep.

But he didn’t hear it. He felt it. The tunnel was not silent: the idling engine hissed and clanked, dripped and cracked at random as he progressed along its metal flanks. Any rustling in the tunnel would have to work hard to make itself heard above the cacophony.

Even now, he still couldn’t say which sense was being alerted, but the memory of the feeling was pungent.