They were racing through a narrower tunnel now, close quarters pressing in on both sides. A big bump in the road jarred them, the ATV went airborne for a second and the roll bar banged against the low roof.

Seconds later, they came upon a dead end. “Look out!”

Renata slammed on the brakes and the ATV skidded to a halt. She flicked it into reverse and zoomed backward toward their charging pursuers and then swerved into a side tunnel she’d seen as they passed. She hit the brakes again, spun the wheel and hit the gas. The ATV shot forward into the new tunnel and downward across a sloping rubble field.

It proved to be a huge open room, probably mined for decades. It also had no other exit.

“We have to go back up,” Renata shouted as the headlights played across a stark wall.

She turned them around just as the lights from the following vehicles were growing brighter in the entranceway.

“We’ll never make it,” Joe said.

Renata pulled to the side and shut off the headlights. She kept still as the first ATV came through the entrance and rumbled down the rock-strewn slope. Their lights blazed straight ahead and Renata, Kurt and Joe remained hidden in the dark.

The second car followed. As soon as there was a gap, Renata stomped the accelerator and aimed for the exit. Halfway up, she flipped the lights back on.

The transmission surged and protested as tires spun one moment and grabbed for purchase the next. They pulled out into the tunnel again and headed back the way they’d come.

The chase vehicles didn’t give up, emerging rapidly and closing the gap once again.

“Joe,” Kurt shouted. “Cut me loose.”

Joe reached back and grabbed Kurt’s arms. Holding them as still as he could, Joe slipped a knife under the zip tie and pulled. The plastic snapped and Kurt was free.

He unzipped the waterproof pouch on the front of his wet suit and pulled out the case with the cold packs. Opening it, he pulled out one of the vials.

“Is this what I think it is?” Joe asked.

“Black Mist,” Kurt said.

More gunfire came their way.

“Now what?” Joe said.

“Nap time for the group chasing us.”

Kurt flung the vial at the wall as far as possible behind the vehicle. It shattered on impact and spread its contents through the tunnel, causing the glare from the headlights of the ATVs pursuing them to dim momentarily.

The chase vehicles burst through the Mist as the lights of the lead car veered off course and hit the wall. It bounced off, turned sideways and tumbled. The second pursuit vehicle rammed it and the men were thrown from the seats and scattered into the tunnel. They didn’t get up.

Renata kept the pedal to the floor and the wreck was soon far behind them.

“Handy stuff,” Joe said.

“We can’t use it all,” Kurt replied. “We need to get it to a lab so it can be analyzed.”

“Is that why it’s packed in ice?”

“The guy told me we had eight hours or it would degenerate.”

“That was nice of him,” Joe said.

“He wasn’t a bad guy,” Kurt said. “Just in over his head.”

Up ahead, the tunnel split in two. Lights could be seen reflecting down the curving section on the left.

“Always traffic when you don’t need it,” Renata said. She veered right. This tunnel took them up, where it split again and dumped them into a much wider tunnel. She continued on and found several more offshoots, some going up, others going down.