“That’s everything,” he said. “Maybe they’ll think we got out through the fires.”

Remi shook the bag. “Are you able to carry this?”

“It’ll make a good weight.” He removed the lead weights from his belt and attached the bag to it.

Sam and Remi put on the rest of their dive equipment, held their flashlights, and sat on the edge of the pool. He said, “I’m sorry it comes down to a long shot.”

She leaned over to bump him with her shoulder. “It’s not such a long shot. If there’s one sinkhole, there are probably others. We just have to conserve our air to give us more time to find one. We should have about twenty-five minutes.”

He nodded. As he did, there was a ferocious barrage of gunfire that ran along the top of the wall on three sides, knocking chips and mortar into the air. Sam and Remi turned their heads to kiss. Then they put on their masks, inserted their mouthpieces, and slid into the water. They swam downward for ten or twelve feet and then felt the slow current catch them and begin to push them gently away.

Chapter 12

GUATEMALA

Sam and Remi swam cautiously in the deepening darkness, just going with the current for about a hundred feet to make sure that no one standing above the cenote could see them turn on their flashlights, and they increased their speed to move along the stone corridor of the underground river. The water rose all the way to the ceiling of the cavern, leaving no airspace above the surface. At first, the walls were about twenty feet apart but thirty or forty feet deep. Each time the space between the walls narrowed, Sam and Remi would feel a growing dread. When the space opened up a little, their relief was intense.

They kicked their fins steadily to keep their speed up, and the current helped them along. They held their flashlights ahead of them, but what they saw was always the same—more curving tunnel. When the tunnel narrowed, Sam would wonder whether it was merely a fissure in the rock opened up by one of the frequent earthquakes in the region. If it was, it could narrow at some point from twenty feet down to six inches, and they would be trapped and drown.