The sonar signature disappeared into white noise as the river turned to the northeast.

Ben kept us in the middle of the channel. Volcanic cliffs rose to either side of the sub, waves crashing against the base of the plateau.

As we ventured farther inland, a blip appeared on my screen as something massive rose off the bottom.

“Zachary, what is it?”

“From its size, I’d guess another Purussaurus, or maybe the same one. It’s still in the vent field, but it’s ascending toward the channel.”

Ben cursed under his breath. “In for a penny, in for a pound.”

The Barracuda accelerated through the chop, our propeller’s signature lost in the whitewater.

“Talk to me, Zach. Can that croc follow us inland?”

“Yes, but that doesn’t mean it will. The entrance is plenty deep. I can’t see anything beyond the first curve. It’s getting a bit rough topside.”

“Got it.” Ben dove the sub, killing our external lights in favor of his night-vision goggles. A Miocene river bed appeared below us in bright green, littered by harrowing outcroppings and boulders that churned the surface at twenty-three knots.

My pulse raced as the Purussaurus entered the channel.

We followed the waterway inland for several miles, the canyon’s walls gradually settling along either side of us into a rocky embankment, the volcanic rock slick with algae.

The sound of rushing water grew louder in my headphones until I was forced to pull them away from my ears. “We’re either approaching rapids or the dispersal zone of a waterfall. Can you back us off?”

“Negative. We’re caught in its vortex. There’s no room to come about. Hold on, boys and girls, we’re going through.”

A thunderous echo of water reverberated through the Barracuda as the river curved to the east, slinging us sideways and grinding the keel against unseen rock as we spun downstream through subglacial rapids, the whitewater tossing our submersible about like a log.

Closing my eyes, I held on in the turbulent darkness, waiting for the sudden rush of freezing water as our inverted cockpit repeatedly bashed against unseen rocks. I thought about Brandy and William and cursed the selfish decision that defied my own fear and intellect. Most of all, I cursed Angus for having manipulated me.

Who was I kidding? The decision to accept the mission had been mine to make. I had forfeited happiness for a shot at immortality, and for that I would pay the ultimate price.

Emptiness replaced fear as I realized I’d never hold my beautiful bride again, never play ball with my son, never walk him to school or watch him grow up or graduate or raise a family of his own. With my death, those responsibilities and the rewards that came with parenthood would be passed on to his mother and whomever she chose to fill the void I was about to leave in her life.