Gray shoved her back out of the shelter. She stumbled, deaf, eyes watering. Overhead, the helicopter swept past, swirling smoke and flames. A black steel barrel was rolled to the lip of the open hatch.

Oh, no...

Panicked, knowing what was coming, Rachel sprinted down the passageway, gasping in pain as she hurdled rocks and sections of tumbled wall. The arched opening gaped ten yards away. Focused on her goal, her heel landed on a moss-encrusted stone. Her foot slipped, and her leg twisted. She stumbled-but never hit the ground.

Gray scooped her around the waist and carried her the last few steps. They dove together through the archway. Bodies shoved into them from behind. They fell as a group, tripping, tumbling down the flight of stone steps.

They landed in a pile at the bottom as the world exploded above them.

The blast, striking near the opening, immediately deafened them. Pressure slammed Rachel's ears and felt like it cracked her skull. Rocks tumbled and bounced. Flames gusted down the throat of the stairwell, washing across the roof overhead. Her skin burned. Her lungs could draw no air.

Then in a rush, the pressure popped. The flames were sucked away, back out of the tunnel. Cool air drafted up from the lower levels and washed over them.

Hands shoved and dragged. They crawled away from the stairs down into the murky lower passages. After a few yards, they all slowly gained their feet. Rachel used the walls to haul herself up. She panted, felt like vomiting, fought the rising gorge. She took great gulps of cool air.

"Keep going," Gray urged.

Rachel leaned on the wall as they stumbled away. They had to keep moving. The concussions and fires could drop the upper level on top of them. They had to get clear.

"Can you find that exit?"

She coughed. "I think...maybe..."

Gray grabbed her elbow. "Rachel."

She nodded, regaining her balance, both inside and outside. "Yes. This way." She pulled out her cell phone and flipped it open. The meager glow didn't cast much light, but it was better than nothing.

Holding on to Gray's shoulder, she set off. It wasn't far, but this level was a rabbit warren of cells, passages, and cave-ins. She headed out, lost in the past as much as the present.

She remembered Uncle Vigor taking her down here, tantalizing her with tales of heroes and monsters, of strange beasts and great pageantry. He had also told her about one of the grandest of shows, a rare event held at the Coliseum. A spectacle called a naumachiae.

She spoke aloud as she led the others. "Before these underground levels were built, early in the Roman empire, they used to flood this area, creating a great lake in the middle of the Coliseum. Famous sea battles were reenacted here, along with demonstrations of swimming horses and bulls."

Kowalski trailed behind them, dusty, bloody, and burned. "Right now, a swim sounds pretty damn good to me."

"What did they do with all the water after the show?" Gray asked.

"You'll see," Rachel said.

Another two turns and they ended up at a wall. An iron grate sealed a narrow, low passageway. Even in the meager light, it plainly led down at a steep angle.

"They cleared this just last year, confirming what Uncle Vigor already knew." Rachel unlatched the gate and pulled it open.

Before she could explain more, a loud rumbling crash echoed across the space. Rock dust wafted in a thick cloud and rolled over them.

"The bombs are triggering a cave-in," Rachel said.

Closer at hand, a marble block fell from the roof a yard away and crashed heavily to the floor. More groans and rumbles followed. Like the first tip of a domino, the entire level was beginning to collapse on top of them.

"This way," Rachel said. "Hurry."

She ducked into the steep passage and led the way down. Behind her the others followed single file. They hadn't taken more than a half-dozen steps when the floor shook, accompanied by an ominous rumble of thunder. More dust filled the air, choking and blinding them.

Rachel hurried onward, covering her mouth with her arm. She felt blindly ahead of her. The steep floor grew even steeper. Rachel used one hand to brace herself and held forth her glowing cell phone in the other.

"How much farther?" Gray gasped out.

She didn't answer. She didn't know.

After a long silent minute, a trickling echo reached her. She rushed onward. In her haste, she lost her footing on the floor, landed on her backside, and slid, losing her cell phone. It skittered ahead of her-then vanished.