Reed kept one M67 grenade. I took the other. It was a standard fragmentation grenade, filled with high explosive and relying on steel fragments for lethality. In open terrain its effect was limited, but inside a confined cavern it could generate a deadly shockwave.
The blue fireballs had closed to less than thirty meters.
I pulled the safety pin, counted two seconds, and threw the grenade toward the densest concentration of cold light ahead. The explosion thundered through the cavern, the shockwave ricocheting along the rock walls. A dozen fireballs were struck by fragments and dropped, extinguished instantly, but more lights continued pressing forward from behind, their numbers hardly reduced.
"Fall back!" Reed ordered.
Eleanor led the direction ahead while the three of us covered the rear, retreating and firing our M4 carbines continuously. Rounds carved brief, blinding streaks through the dark, but twenty-round magazines emptied quickly. Spent casings scattered across the rock, echoes blending with gunfire until they were drowned out by the advancing vibration of wings. These blue fire spheres formed from beetles could only be suppressed at distance; once they touched fabric or skin, ignition was immediate. An empty rifle meant nothing here. Walker dropped his spent M4 and pulled his last M67 grenade, turning back to look at me, something resolute already in his eyes.
"Grant. It's time."
Eleanor and I supported him, the three of us forming a circle. Once the pin was pulled, in seconds everything would end in the blast. The firelight advanced, the air turning rigid with cold, the wingbeats blending into a continuous hum. Just as Walker prepared to move, Eleanor suddenly lifted her head and listened.
"Water," she said. "There's an underground river nearby. If we get into it, they won't be able to ignite us."
Walker stared at the approaching blue flame and muttered, "Next time I'm volunteering for desert duty."
I didn't answer. In the chaos we had nearly forgotten the subterranean river, and now it was the only possible escape. We turned toward the sound of water, the blue flames compressing the space behind us, the cavern walls glowing almost translucent under the cold light. After rounding a rock bend, a waterfall burst into view. Water poured from above into a sizable underground lake below, mist churning in the blue glow. The fireballs were nearly upon us. Heat flared across my back, pain spreading along my spine; a flame had grazed my tactical pack. There was no time to assess the damage. I dove straight into the lake. The surface exploded upward. Water enveloped my body, and the blue fire extinguished instantly on contact. The lake was not freezing. It carried a faint warmth, clearly influenced by geothermal activity. The fireballs hovered two or three meters above the surface, circling, never daring to descend.
I surfaced for air. Reed emerged seconds later. Eleanor dragged Walker up; he had inhaled water on entry and nearly blacked out, but she pulled him clear before he slipped under. He coughed violently and regained consciousness. Above us, countless blue flames lit the cavern like daylight. The four of us gathered together, minimizing the parts of our bodies exposed above the waterline.
"My rifle's at the bottom," Walker gasped, glancing at the circling fireballs. "At least they don't swim."
"Don't give them ideas," Reed said quietly.
Before the words fully left his mouth, the fireballs began to change. Thousands of lights gathered rapidly overhead, merging into a single massive sphere dozens of meters across, its energy density far greater than their previous individual form. It angled downward toward the lake.
"Dive!" I shouted. We submerged again. The massive fireball struck the surface, generating a burst of steam and violent turbulence. But the volume of the lake far exceeded the energy of the flame. The beetle-like attackers lost combustion capability upon contact with the water and sank to the bottom. The lake gradually calmed. Underwater, I opened my eyes. Residual blue light filtered through the surface, illuminating the lake floor more than ten meters below. Large numbers of massive fish moved slowly in the depths, their bodies elongated, whiskers trailing, eyes reduced to milky points, clearly adapted to total darkness.
I surfaced again to breathe. The lake was covered with drifting beetle carcasses. The firelight was gone. The cavern sank back into heavy darkness.
"Anyone have light?" I asked.
"Lost mine," Walker replied.
A beam snapped on.
Eleanor stood waist-deep in the water, holding a military angle-head flashlight. "Two more secured inside the vest."
We climbed onto the rocks along the shore, exhaustion overwhelming us. Hunger became real. Reed went back into the water, drove his M9 bayonet into one of the large fish, and dragged it ashore. After a simple field dressing, we divided the meat. It tasted faintly bitter but restored strength. After a brief rest, I moved along the shoreline searching for an exit. The waterfall fed too much volume for this lake to be closed. Soon I found a break in the rock where the water flowed out through a passage seven or eight meters high. The floor was completely submerged, leaving no path to walk. I reported back to Eleanor. Her map and compass were gone; she had only terrain judgment and water flow direction.
"We follow the water," she said. "Rivers don't end in dead walls."
We entered the water again, the three stronger swimmers keeping Walker between us as we moved downstream. The underground river was not wide, but the current was strong enough to carry us forward without effort. The temperature was rising. The air carried sulfur. Even submerged, the dryness and heat could be felt. We swam for a long time with no sign of an end to the passage. Then Eleanor suddenly turned.
"Something behind us."
The water surface began to churn abnormally. I turned and swept the flashlight beam across it. The light trembled on the ripples. A massive dark shape was approaching rapidly from downstream, far larger than the fish we had seen before. Walker stared at the incoming silhouette, his voice barely audible.
"Please tell me that's just a really big trout."
We almost simultaneously drew our M9 bayonets.
The vibration in the current intensified.
Whatever it was, it was closing in.