Aimee rested her back against the red granite and tilted her head up towards the dark domed ceiling. “Well, my father always said people with brains will rise to the top—boy, I’m glad he can’t see me now, miles below the surface of the world. Fact is, I’m a science nerd. While all my friends were going to the beach to lie on the sand and improve their tans or rub lotion on their boyfriends’ backs, I was over in the rock pools turning over stones to look at the tiny creatures. My grades were always good and after sailing through chemistry and biology, I got hooked on solving the world’s energy problems by creating a biological synthetic fuel. Except I didn’t know I was working for the U.S. Army until a week ago. Not sure it would have mattered; sure doesn’t now. Now it seems such a small issue, as if it belongs to someone else while we’re all hiding down here in the dark.”

She smiled at Alex and moved a little closer. He noticed the set of her jaw was still strong. She’s a brave woman, he thought. A strand of her hair had fallen out from under her helmet and hung across one of her blue eyes. He wanted to reach out and push it back behind her ear but stopped himself. His eyes saddened as he thought, she can never know me.

“We better start climbing again, we’re nearly home.” Alex walked away.

They climbed the ramp to the upper doorway, the silence broken only by their soft footfalls. Dust gently floated in the beam of their lights, making the rays stand out like wide lasers in the pitch darkness.

Aimee shivered—it was much colder here. “Look.” She exhaled and her breath created a small fog in the light beam. “We must be closer to the surface now.”

Alex pulled his stratigraphic sonar from his backpack and pointed it at the roof. After a few seconds the small screen lit up with the readings he was seeking. “Still says we’re about a mile down, but I can’t tell how deep we are in the catacombs, how much is rock or how much of that is ice.”

Matt turned back to the group after reading the carved glyphs in the wall. “Could be a problem—the Aztlans seem to be similar to the Olmecs or Aztecs, who made extensive use of caves. Some of their artifacts and burials have been located many miles deep inside cave systems. My guess is they had been exploring and excavating the underground cave system for hundreds of years. They were obviously adept at stone cutting, so could easily have dug down many levels, perhaps miles. They could also have found the cave system and simply modified it for their use, which means this could be very deep indeed.”