“We’re in a mine,” he said. “See the chisel marks?”

“This could be the source of the gold that the hotel guests panned for.”

Zavala probed the darkness ahead his light. “Look.”

A tunnel opening had been cut in the wall to the left.

They left the main cave to explore the tunnel. The passageway was about ten feet high and six wide. A barrel ceiling arced overhead. Alcoves had been cut in the wall for torches.

After about a hundred yards, the tunnel intersected with another at a right angle. The discussion of their next step was short but intense. They could be dealing with a labyrinth. Without a lifeline, they could quickly lose their way. The limited amount of air in their tanks could make the wrong decision a fatal one.

“Your call,” Zavala said.

“The floor on the right-hand passageway is more worn than the others,” Gamay said. “I say we follow it for a hundred yards. If we don’t find anything, we’ll head back.”

Zavala crooked his forefinger and thumb in an okay signal, and they plunged into the passageway. They swam without talking to conserve air. Both were aware that each fluttering kick brought them closer to danger. But curiosity spurred them on until the tunnel ended, and they broke into the open after swimming about fifty yards.

The passageway had ended in a large chamber. The ceiling and opposite walls were beyond the range of their lights. They had come to the most hazardous part of their dive. It would be easy to become disoriented in a large open space. They decided to confine their exploration to no more than five minutes. Gamay would stay at the mouth of the tunnel. Zavala would do the actual exploration. At no time would one diver be out of sight of the other’s light.

Zavala struck out into the darkness, keeping close to the wall.

“Far enough. I’m losing you,” Gamay cautioned.

Zavala stopped.

“Okay. I’m swimming away from the wall. The floor is smooth. This room may have seen a lot of traffic. Nothing to indicate what it was used for.”

Gamay issued another warning. He turned back and homed in on her light. He followed a zigzag pattern that would cover the maximum about of ground.

“See anything yet?” Gamay said.

“Noth—wait!”

He swam toward an amorphous shape.

“You’re moving out of sight,” Gamay said.

Gamay’s beacon had become a smudged pinpoint. It would be suicide to proceed much farther, but Zavala couldn’t stop now.

“A couple more feet.”

Then silence.

“Joe. I can barely see you. Are you all right?”

Zavala’s excited voice came over the communicator. “Gamay, you’ve got to see this! Leave the torch to mark the tunnel and follow my light. I’ll wave it.”