Marty and Elsa continued in the direction they had been heading when they’d encountered the first merfolk. They had planned this course of action before diving for the assault rifle. Their reasoning had been that it would take them nearly thirty minutes to return the way they had come; that was a hell of a long time to be in the water, even with the protection of the firearm. Moreover, they would be all but helpless when passing through the tight restrictions, unable to turn around and fight back.

Continuing forward, on the other hand, was a gamble. They could encounter dead ends, become lost, or run out of air before finding their way to the open ocean. Yet given the alternative of being skewered with a spear, it was a gamble they were willing to take. Chances were good, they’d reasoned, that they were close to the exit. The distance they had already traveled and the strong currents they had experienced suggested it—not to mention the presence of the merfolk. Early humans holed up in the mouths of terrestrial caves rather than deep within the systems to be close to their hunting grounds, and Marty had assumed the same likely held for merfolk as well.

Elsa was in the lead, with Marty close behind her. The pain in his side had subsided, and he believed the wound was not as bad as he’d initially imagined. Every ten or twenty seconds he would glance behind them and expect to see any number of merfolk following in pursuit. There were never any there. The assault rifle had apparently scared them away for good. This was not surprising, as it had decimated one of their kind before their eyes. While white sharks and orcas and other pinnacle predators had formidable jaws that could tear them apart, those jaws had to catch them first. Marty simply had to point a strange device at them, and they were dead. The risk-reward trade-off was simply not worth it.

Elsa was looking back at him and pointing to the floor of the lava tube.

Parts of it were covered with scattered pockets of sand.

Marty experienced a wave of overwhelming relief, but he wasn’t going to celebrate until they were out of the water and on dry, solid land.

Rather quickly they began to see coral and urchins growing on the solidified lava, as well as small fish swimming in schools. Then there were no longer walls to either side of them, and the midnight-black water lightened to something slightly less opaque.

They surfaced at the same time. Marty shoved his mask up his forehead and removed his respirator from his mouth. The star-filled night sky had never been so big or beautiful.

Elsa removed her respirator and blurted, “We made it!”