The system comprised a folding stand with a single wheel on the front and two in the back, like a modified baby stroller. An operator console with a screen rested at chest level in front of the handlebars, with the sonar detection array suspended just above the ground near the front wheel. The soldiers watched them with mild curiosity as they pushed the assembled cart to the dirt ramp. Antonio stopped and chatted with them, explaining that they were conducting measurements below and not to worry. Nobody seemed interested, and soon Sam was fiddling with the device controls to calibrate the sensitivity.
“See that? Solid earth,” he said, pointing at the screen, which was a sea of static.
“How will we know if it’s not solid? Or if it’s structure?” Remi asked.
“That’s where the art comes in. It will all depend on the operator’s deft touch.”
They inched slowly along the passageway toward the crypt, and Sam turned knobs as they progressed. Three-quarters of the way to the chamber, he stopped and adjusted the screen.
“What is it?” Maribela asked.
“Looks like something below us. Yes, there’s definitely something there.” He pointed at the screen. “See that? The disturbance in the field? It’s a hollow area. Could be a cave . . . or a tunnel.”
“A cave?” Remi asked.
Antonio nodded. “Yes, much of the city was built above caves. The Pyramid of the Sun, for example, has a naturally occurring cave beneath it that was used for sacred rites.”
“So how do we know whether it’s man-made or natural?”
“Lazlo, would you take the chalk and mark this position? We’ll come back to it later,” Sam said, indicating a tin of yellow powder. Lazlo made an X on the dirt floor, which everyone was careful not to disturb as they continued toward the chamber. Just outside, the floor became stone blocks and Sam had to recalibrate the system again.
They passed over the threshold and carried out a methodical grid search of the tomb area, but there were no more readings like the one in the passageway. After twenty minutes of careful scanning, Sam wiped a bead of sweat from his forehead and motioned to the tunnel.
“The only thing I’m picking up is that one anomaly on the way in. That’s it.”
“It didn’t seem that big, did it?” Maribela asked.
“No. No more than a couple of meters.”
“How far below us?” Lazlo asked.
“Looked like maybe two, two and a half meters. We’ll be able to narrow it down once we go over it again,” Sam explained, and then pushed the cart back into the passageway and stopped at the chalk mark on the ground.
“There it is. It’s two meters directly beneath us. Looks irregular—wider than it is long. Could be just about anything, but it’s definitely there if you’re feeling adventurous.”
Remi’s eyebrows rose. “What did you have in mind?”
He studied the image one final time before shutting the system off.
“I was thinking a little exercise might be invigorating.”
Sam, Antonio, and Lazlo grunted as they swung picks at the hardened clay, having hit a rhythm over the half hour they’d been working at it. Twice they’d stopped and cleared away piles of soil, and they were now halfway to whatever awaited them, standing in a hole roughly eight feet square. Remi and Maribela piled the dirt evenly along the wall, to be filled back in once they’d satisfied their curiosity about the mysterious cavity beneath the corridor.
The earth below the men’s feet began to shift and before they could climb out of the pit it gave way. They found themselves falling in a shower of dirt and then landing on a stone floor hard enough to knock the wind out of them. Remi’s voice drifted down to Sam from above.
“Are you all right?”
Sam shook the dirt off and sat up, probing his ribs before calling out to her.
“I think so. Lazlo? Antonio?”
Antonio shifted next to him. “I’m okay. Just . . . stunned.”
“No way to treat guests, I’ll say that much,” Lazlo muttered, brushing dirt off his face.
“I thought we’d have more warning than that before the floor gave way,” Sam said.
“Sometimes it’s an imprecise science, no?”