Just at that moment another explosion sounded above my head. My heart hammered against my ribs and my calves felt wobbly. I forced myself to stand still, not to give away my presence by jumping or fleeing back up the hall. And in another second I felt like a fool: the motor operating a huge gantry had sprung to life, its gears clanging like a foundry under full steam.

The gantry’s tracks crisscrossed the room’s high ceiling. They ran parallel between a wide concrete shelf built about two-thirds of the way up the wall and the doors to the bays. Two perpendicular tracks, each with a gigantic crane hanging from it, connected the two. Presumably the concrete shelf led to a storage area.

When I’d been here before I’d noticed iron stairs at the main entrance leading to a second story, probably the same area fed by the gantry. It didn’t seem very efficient to me, keeping heavy materiel on the second floor when your work was all down below. Still, that might be the best they could do with the constraints on their space; the construction around the canal was so tightly packed that they couldn’t expand sideways.

As I squinted in the dim light to follow the crane’s route I noticed movement above me. Someone had emerged from the gloom of the upper deck and was climbing down a steel ladder built into the wall. He didn’t look around but headed straight for the bays and began unlocking the doors.

I began to feel uncomfortably exposed and started a backward retreat up the hall. Just as I moved from the doorway the loading cavern was flooded with light.

I looked nervously over my shoulder. No one was behind me. I turned and sprinted up the corridor, hugging the south wall to stay as far from the sightlines in there as possible.

When I got back to the main hall I stopped to catch my breath and reorient myself. A right turn would lead me to a T crossing; a couple of turns there and I’d find myself back in the administrative offices. Or I could go left, which would bring me to the front entrance with the iron stairs leading upward.

The trouble was that I wanted to see both places. People loading trucks in the middle of the night at what appeared to be a deserted factory deserved a closer scrutiny. If I chose the office first they might finish whatever they were doing with the trucks before I got back to them. On the other hand, if someone saw me watching the trucks I’d have to flee without seeing Chamfers’s files. Choices, choices. I turned left.