Karen pointed to the walls on either side. “Stone blocks,” she said. Here the walls and ceiling were no longer bare rock, but stacked and carefully fitted basalt slabs and blocks. “We’re above the lava tube.”

“So we won’t drown?” Miyuki looked pale, her ebony hair wet and clinging to her face.

“Not if we climb high enough. Get above sea level.”

Miyuki stared up the staircase. “But where are we?”

“If I had to guess, I’d say these steps lead into the heart of the second Dragon, the twin pyramid to the one we entered.” At least, she hoped so. But it made some sort of symmetrical sense. And if she wasn’t mistaken, the passage had been heading in the direction of the other pyramid. The lava tube must connect the two structures.

“Will there be a way out?”

Karen nodded. “I’m sure there is.” She left unspoken her own fear. What if they couldn’t find it?

“Then let’s go,” Miyuki said, shoving herself to her feet. She reached toward Karen. “I’ll carry the bag from here.”

Karen pushed the strap off, only too glad to shed the burden, and passed the bag to Miyuki, who almost dropped it.

“You weren’t kidding that it’s heavy,” she said, straining to heft it to her own shoulder.

“Nope. It’s that crystal artifact. It must weigh close to ten kilos.”

“But it was so small.”

Karen shrugged and stood up. “Just one more mystery about this place.” Sighing, she led the way up, praying that the final mystery would not escape her: the way out of this death trap.

The climb up the steep stairs was a cruel torture for their aching limbs. It felt like they were climbing a ladder. But they plodded onward, silent, too tired to talk. At least the exertion served to warm their cold bodies. But soon even the warmth became a burden. With each step the temperature seemed to rise in the narrow stairway. By the time they neared the top of the stairs, it was stifling. It seemed to Karen that her damp clothes were steaming.

She wiped the sweat from her forehead and entered the next chamber. “Finally,” she moaned as she shuffled into the room. Miyuki followed her, wheezing. Karen raised her small flashlight.

The bare walls of the inner chamber offered no clue to an exit. Stacked stones and a slab roof surrounded them. Both women gazed around. There were no adornments, no writing.

Karen moved along the margins of the walls. “Turn off your light,” she ordered Miyuki. Karen flicked her penlight off, too.

Darkness plunged around them. The echo of splashing water from the passage below seemed to swell. With eyes wide, Karen looked for a chink in the solid walls and ceiling. Some evidence of an exit. By now she assumed the sun would be sliding toward the western horizon.

She mopped at her brow. It was so warm in there. Not a bit of air moved. With one hand on a wall, she edged around the room, searching for a telltale glow, some sign of an exit. But the darkness seemed complete.

“Are you finding anything?” Miyuki asked, hopeful.

Karen had opened her mouth to answer when her hand touched a stone warmer than the others. She paused, placing one palm on one stone and the other on its neighbor. There was a clear difference in temperature.

“I think I may have a clue here.” She fingered the edges of the warmer stone. It was difficult in the dark. The blocks had been fitted snugly. She discovered the edges, but as she stared, found no sign of sunlight creeping through. She frowned. There had to be a reason for the warmer stone.

Karen thumbed on her penlight, and Miyuki moved to her side, resting her bag on the stone floor. She rubbed at her shoulder. “What did you find?”

Karen shoved hard on the stone. It didn’t move. She backed up a step, head tilted, studying the stone block. It was featureless, about half a meter square. “This is warmer than the others, suggesting it must be more directly exposed to the sun.”

“Is it a way out?” Miyuki turned on her own flashlight.

“I hope so. I just don’t know how to open it.” Karen closed her eyes. Think, goddamn it! She pictured the second Dragon in her mind. It was identical to the first, except for the collapsed temple. This second pyramid’s summit had been bare. No clue.

“What are you thinking?” Miyuki asked.

Karen opened her eyes. “I’m not sure. In the other pyramid, the temple’s altar was the access point. The sculptured snake head was the key.”

“Yeah?”

“Think symmetry. Think larger. In the ruins of Chichen Itza on the Yucatan peninsula, the main pyramid casts a snake shadow during the equinoxes, a winding shadowy body that connects to a carved stone snake head at its base.”

“I don’t understand.”

Karen kept talking, intuiting that she was close to an answer. “The serpent’s head was the entry point. This connected to a long lava tube…perhaps representing a snake’s body.”

Miyuki nodded. “If you’re right, then we’re in the snake’s tail.”

“We were swallowed by a snake, traveled through its belly, and now must complete the digestive process.”

“In other words, we must find this snake’s butt.”

Karen laughed at the dead seriousness with which Miyuki had spoken these last words. “Yep.” Karen turned. The opening to the stairwell lay directly opposite her. She twisted around. The warm stone was in direct line with the opening. A straight line. She placed a hand on the stone. “This is the tip of the tail. The end of the snake.”

“Right. You said that. It’s the way out.”

“No! We aren’t paying attention to anatomy. A snake’s butt isn’t in the tip of its tail. It’s on its underside!” Karen pointed to the floor. “Its belly!”

Miyuki stared at her toes. “To go up, we must go down.”

Karen dropped to her knees on the stone floor. It wasn’t a slab, but fitted blocks, like the walls. She crawled forward, starting at the warm brick and aiming for the stairwell, wiping the water and debris from the floor as she went. It had to be here!

Her fingers brushed over something rough on the smooth stone. She froze for a heartbeat, then rubbed the spot, praying.

Miyuki knelt near her. “What is it?”

Karen moved aside. “The snake’s butt!”

Imprinted into the smooth block was a carving: a star-shaped depression.

“Get me the crystal!”

Miyuki rushed over and retrieved her bag. She dragged it back, then zipped open the side pouch and pulled the star-shaped crystal out. She had to use both hands. Grunting, she hauled it over to Karen. “Here.”

Karen rolled to her belly and lugged the star into place in the depression. It was a perfect fit. She held her breath, ready for anything. Miyuki stood by her shoulder, a fist at her throat.

Nothing happened.

Karen sat up on her knees. “What’s wrong? What aren’t we doing right?”

“Maybe the mechanism is broken.”

Karen did not even want to think of that possibility. She knew that by now the lower passage must be totally flooded. There was no way back. They were trapped here. She felt tears coming to her eyes. Her throat tightened.

“How was the crystal supposed to trigger the secret passage?” Miyuki asked, still pondering the riddle.

“I…I don’t know.”

“Didn’t you say something about the other mechanism being pressure-sensitive?”

Miyuki’s words sank through Karen’s hopelessness. She remembered how the altar stone had moved back up into the ceiling after Miyuki had jumped off it. The mechanism must have been pressure-sensitive, responding to the change in weight.

Karen stared down at the crystal. It was heavy, unusually so. But if the secret door here was triggered by weight, then why hadn’t it triggered when she’d first walked across it?

Then it dawned on her.

“Get off! Get off!” she yelled at Miyuki, waving her away from the stone block and crystal. “We weigh too much!”

“What?” Miyuki said, but backed away.