Zavala suggested that they push higher for more leverage. They slid their feet to the ends of the rods, planted their backs and tried again. This time the slab went over so fast that they almost tumbled down with it. It crashed in slow motion off a big boulder, breaking in half, then bounced a few more times before landing in a muddy cloud. Several other chunks followed it down in a secondary landslide.

“Crude but effective,” Austin said, as he drifted down the face of the pile and stopped in front of a newly created opening in the rubble. He probed the hole with his light, then tried to squeeze through only to have his air tanks get in the way again. He removed the tanks. Keeping the regulator in his mouth, he backed into the opening feet first and pulled his tanks in after him. Zavala followed using the same procedure.

They were wedged in a tight space between the pile of boulders and two massive steel blast doors. The armored doors were sealed, but near the top of one was a shadow where the force of the explosion had peeled back a comer like a page in a book. The gap was big enough for them and their tanks. They slipped through the hole and flashed their lights around. The beams faded into nothingness except for a grayish reflection over their heads. They swam up several feet until their tanks scraped against concrete. Swimming a few feet below the ceiling, they proceeded through the murky water.

After a few minutes, the ceiling disappeared and they swam up until their heads emerged into the open. They were in complete darkness. Austin removed the regulator from his mouth and took a tentative breath. The air was musty but breathable. They switched on their lights and saw that they were near the edge of a man-made pool. They swam to a ladder, pulled themselves up on the side of the pool and flashed their lights around, probing the perimeter of the rectangular basin.

“Hel-Io,” Austin murmured. “Someone left their rubber ducky in the bathtub.”

His light outlined the contours of a submarine on the far side of the pool.

They stacked their scuba gear in neat piles for quick retrieval and stripped down to their lightweight black insulated liners. They were traveling light, taking only their weapons, extra ammunition and lights and, in Austin's case, a belt radio. He tried to call Kemal, but the thick concrete walls made radio contact impossible. Setting off to explore the high-ceilinged chamber, they followed a set of narrow-gauge tracks that ran around the pool's perimeter, making their way past fuel pumps and conduits for water and electricity.