T o Tyler, it seemed as though they’d been in the tunnels for days, but his watch told him it had been little more than an hour. Halfway through, a dull peal, like thunder, had echoed off the walls. It had to be the booby trap Orr had implied when he said he was leaving a nasty surprise for Cavano. Orr even smiled with satisfaction at the sound. Tyler just had to hope Grant had gotten the warning he’d risked writing on a piece of paper torn from the codex translation.
Only a few of the passages were as narrow as the first one, so all four of them often walked through together. At one point, Tyler had caught Orr scratching a mark on the wall of a passageway they’d just come through, presumably so that he could find his way out again. Orr must have been confident that Cavano would be in no condition to trail them, but Tyler made himself believe Grant had survived the explosion and would be following the marks.
Archimedes had made the operation of the geolabe intuitive only to someone who understood his mathematical reasoning. Once Tyler had solved the formula in the codex, the usage of the geolabe was relatively simple, but he wasn’t about to tell Orr that.
Most intersections had four offshoots, but some had three and some had five. To find which direction to go, the top knob would be rotated clockwise so that the top dial would move the same number of zodiac marks as the number of openings at the intersection. The bottom knob would be rotated by the same number, but counterclockwise. Then Tyler would flip the geolabe over, and the dial on the opposing side would show the correct direction to go, with the six o’clock point indicating where they’d come from. After the tenth intersection, Tyler still hadn’t seen the dial point to the six o’clock position. As long as the geolabe wasn’t telling them to backtrack, he was confident that he had interpreted Archimedes’ instructions correctly.
Twice they came across cisterns that were still partially filled with water. Tyler guessed that the tunnels occasionally flooded with rainwater during downpours. Maybe the aqueducts had been filled with water only part of the time, which would have made the trek that much easier for Archimedes’ spy.
As they walked, he kept an eye on Stacy. She had withdrawn, saying only the minimum to keep on the path. Several times she seemed on the verge of saying something to him, but then she closed her mouth and looked away. Embarrassment, anger, fear-Tyler couldn’t tell the reason, but she didn’t need to apologize for anything. In fact, he realized an hour ago that he should apologize to her. After playing the events of today back in his mind, Tyler remembered another event that convinced him of Stacy’s innocence. Tyler would let Orr’s charade continue as long as he could, but at the right time he had to go on the offensive, and when he did, he would need Stacy’s help.
Around the next corner, the passageway ended at the midsection of a steeply inclined tunnel leading up to the left and down to the right. Throughout the walk, the group had gone up or down a few steps, but overall they had stayed on essentially the same level underground. The upward direction of the tunnel abruptly ended at a brick wall.
“What the hell?” Gaul said.
“How old do you think those bricks are?” Tyler asked Stacy.
“At least two thousand years.”
“Maybe they didn’t want anyone to find Midas’s tomb,” Orr said.
“Then why leave the passage we just came through unsealed?” Tyler said.
“I don’t know. You’re the engineer. You tell me.”
“It may have had nothing to do with Midas,” Stacy said. “The tablet said that the Syracuse king’s spy was looking for a way into the Roman fortress. Maybe this leads into it, and the people inside were trying to keep invaders from doing exactly what he was trying to do.”
“It doesn’t matter,” Orr said. “Looks like we go farther down the rabbit hole.”
The tunnel extended downward for another two hundred feet, and they emerged into a room twenty feet long and ten feet wide. At the far end was a pool of water that ran the width of the room and was three feet across. What looked like a foot-wide stone bridge spanned the middle of the pool and ended at the wall. Tyler turned in all directions, but there were no more tunnels.
It was a dead end.
“Is this some kind of joke?” Orr asked.
Tyler looked at him in surprise. “No. This is where the geolabe said to go.” Could he have interpreted the instructions incorrectly?
“If this is it, Tyler, I’m going to press my button. You better come up with something fast to make me think you haven’t been screwing with me this whole time.”
Tyler was acutely aware of the explosive belt digging into his stomach as he walked to the far end and inspected the wall.
A nearly invisible crack stretched across the end wall at a height of six feet. The surface was made of the same tuff that they’d seen throughout the tunnel system, but in some places the pocked gray stone revealed a white layer underneath, as if the tuff were merely a thin veneer. Tyler scratched at the white material with his fingernail, but it didn’t flake away like the tuff. In fact, it abraded his nail, almost as if…
Tyler flipped the geolabe over. The dial was pointing to Aquarius, the water bearer. That had to be a clue.
“What is it?” Stacy said.
He dropped to his knees and held the lantern over the water, which became opaque five feet down, obscuring the bottom.
Tyler smiled at the engineering ingenuity of it.
“Eureka,” he said quietly.
“What?” Stacy said.
“Feel that,” he said, pointing to the white stone under the tuff.
She rubbed it with her finger.
“What’s going on?” Orr said.
“It feels like what I use to smooth my feet,” Stacy said. “Pumice?”
“Right,” Tyler said. “Did you know that pumice is up to ninety percent air?”
“Why does that matter?” Orr asked.
“Because it’s the only rock that floats. It’s ejected by volcanoes like Vesuvius. It floats so well that some scientists theorize that plants and animals might have migrated throughout the Pacific on pumice rafts created by Indonesian volcanoes.”
“And your point is?”
“The whole wall below this crack is made of pumice. The tuff on the front is merely to disguise it. The wall is floating.”
Orr looked confused, then glanced down at the water. “Is that possible?”
“Bricks of pumice could have been cemented together. When the pool of water below was filled, the guides in the side wall kept the end wall in place as it rose with the water until it was firmly seated against the ceiling.”
“And no one would ever know it was actually a door,” Stacy said incredulously. “It makes sense that Midas would have made sure his tomb was protected. Grave robbers were a bane to the ancient world, especially because so many kings insisted on being buried with vast hoards of treasure.”
“Like the pharaohs.”
“Wait a minute,” Orr said. “When Gia and I found the chamber twenty years ago, there wasn’t any door.”
“This pool is probably fed by a spring so that it can be refilled. If there was a drought the year you visited, the level in the pool could have lowered enough to drop the barrier.”
Orr got a faraway look in his eye. “Now I remember. We came down an incline and then crossed a bridge over water. I’d forgotten that detail. This has to be it.”
“Can we swim under it?” Gaul asked.
“I doubt it,” Tyler said. “That would make the floating wall superfluous.”
“Then how do we open it?”
“There must be a lever of some kind to release the water,” Tyler said. “When it flows out, the barrier will lower and let us through.”
Tyler walked around the room and saw no sign of any kind of button, switch, or handle.
Then he realized where it must be.
“It’s in the water. Something like the stopper in a bathtub. Take it out, and the water will drain. Take the belt off me and I’ll open it.” If he dove in with the belt on, the electronics might short-circuit, setting off the bomb.
“No,” Orr said. “I don’t trust you. What if there’s an escape route?”
“It’s the only way to get through,” Tyler said, looking at Orr and Gaul, “so I guess one of you has to do it, then.”
“No,” Orr said again. “Gaul, undo Stacy’s belt and give her a flashlight.”
Stacy fixed him with a hateful stare when she realized that she was the one who would dive into the liquid gloom.