The hole appeared to be a cave mouth, set into the smoothness of the wall, around two metres from the base. Clay hauled herself up to take a peep inside, and then dropped back.

“It’s empty,” she said, “but there are stairs leading down.”

I walked forward.

“Stairs?”

“You can see them by the light from the walls.”

“Weird.”

“Yeah.”

“Should we take a look?”

“Nah.” She flicked the suggestion away with her fingers. “We should press on to the crash site. There might still be someone there.”

Preston looked dubious. “If there were, those gunmen would have found them.”

“Not necessarily. The Geest van Amsterdam was a big liner. Plenty of places to hide in a wreck that size.”

“For a week?”

“I don’t see why not. We’ve pulled people out of wrecks after more time than that. As long as you’ve got water, you can survive for two, maybe three weeks without food.”

The boy turned to me for support. “What do you think?”

I looked at the cave’s darkened maw, and it took a few moments for my eyes to adjust enough to make out the pearlescent glow of its walls.

“I think we should press on to the wreck.” If Sudak lived, the chances were she’d still be close to the crash site. Only an idiot would have wandered into this maze-like jumble of canyons through choice.

Preston looked disappointed. “Well, I think we should go back to the shuttle and wait for the Trouble Dog,” he said. “This place gives me the creeps.”

He took a pace back along the canyon in the direction from which we’d come. The shuttle lay around four kilometres behind us, lost to sight around several corners. We had left it sitting in a shaft of sunlight like a housefly warming itself in a gulley. And afraid of being unable to find our way back through the maze, we had left the power switched on so we could home in on its transponder. Compared to the alien landscape we stood in, the idea of the shuttle’s warm cabin seemed safe and inviting, and I could understand why the kid wanted to retreat to its cramped familiarity.

“We shouldn’t split up,” Clay said. “And besides, you’re supposed to be the medic. We need you.”

Preston turned to her. “I’m not a medic.”

“You’re more of a medic than I am.” She jerked a thumb in my direction. “And you’ve got this guy to help you.”

“That’s ridiculous! I—”

A bright light stabbed down from above. Clay yelled, “Get down!” and pulled us both into a crouch against the wall. A moment later, the ground trembled.

When I thought it might be safe to look up again, nothing had changed.

“What was that?”