Kholkov considered this for a moment. “You’re sure there was nothing?” he asked the divers.

Both men nodded, and Kholkov turned to the man who’d suggested the river tunnel. “Take Pavel, rope yourselves off, and search the tunnel for any sign of them.”

The man nodded, moved to the end of the pier, and began uncoiling a rope.

“Search the sub,” Kholkov ordered the divers, who both replaced their regulators and dove.

Sam watched their lights move along the hull until they stopped at what he assumed was the cockpit dome. The lights wobbled and shifted and there came a faint clinking of metal on metal. After three more minutes, one of the men broke the surface and pulled the regulator from his mouth.

“It’s a Marder,” the man said. “The 77.”

“Good,” Kholkov replied.

“The bolts are frozen, though. We need the crowbar.”

One of the men on the pier kneeled beside a backpack and pulled out a crowbar. The diver swam over, took it, and dove again.

There were five more minutes of muffled metal-on-metal banging, then silence for a few moments, then suddenly a giant bubble burst on the water’s surface.

The minutes ticked by until finally both divers broke the surface again. One of them gave a hoot and lifted an oblong object from the water.

“Bring it!” Kholkov ordered. When they reached the pier he knelt down and took the object, which Sam could now see was an all-too-familiar loaf-shaped wooden box. Kholkov studied the box for a full minute, turning it this way and that, peering closely at its surface, before carefully lifting the lid and peeking inside. He closed it and nodded.

“Good work.”

From the river tunnel, a shout: “Help! Pull us in, pull us in!” Several of the men rushed down the pier and began hauling the rope hand over hand. After ten seconds a man appeared at the end of it. Lights panned over him. He was semiconscious, half his face covered in blood. They pulled him onto the dock and laid him flat.

“Where’s Pavel?” Kholkov demanded. The man mumbled something incoherent. Kholkov slapped him across the face and grabbed his chin. “Answer me! Where’s Pavel?”

“The rapids . . . the line got cut. . . . He hit his head. I tried to reach him, but he was gone. One second he was there, then he was gone. He’s gone.”

“Damn it!” Kholkov spun around, paced halfway down the pier, then spun back. “Okay, you two carry him and get back to the lagoon.” He pointed to the other man. “You and I will set the charges. If they’re not already dead, we’ll bury the Fargos alive! Get moving!”

CHAPTER 19

Kholkov and his men left. Gesturing for Remi to follow, Sam scrambled down the rope, shifted his weight back and forth to get a swing going, then nodded to Remi, who jumped off onto the catwalk, followed by Sam. They knelt down together.

“You think he meant it?” Remi whispered.

“I doubt they have enough explosive to bury us, but they can certainly seal the main entrance. Did you check for an opening up there?” he asked, nodding at the tangle of roots.

She nodded. “It was nothing but a crack—no wider than a couple inches, and a good six feet to the surface.”

“But you saw daylight?”

“Yes. Sun’s going down.”

“Well, exit or not, at least we’ll have an air shaft—but they’ve got the damned bottle.”

“One thing at a time, Sam.”

“You’re right. Let’s get off this catwalk before the—”

As if on cue there came a whump from the main cavern, followed by two more in quick succession.

“Down!”

Sam pushed her to the ground and lay on top of her. A few seconds later they felt a gust of cool air wash over them. A cloud of dust billowed through the tunnel and filled the cavern, the heavier particles peppering the surface like rain. Sam and Remi looked up.

“Ah, alone at last,” Remi murmured.

Sam grinned, stood up, brushed himself off, and pulled her to her feet. “You want to stay for a while?”

“No, thanks.”

“Well, then we better get busy on our escape pod.”

Remi put her hands on her hips. “What’re you talking about?”

Sam unclipped the flashlight from his belt and shined it in the water, illuminating the sub’s hull. “I’m talking about that.”

“Explain, Fargo.”

“I’ll check to be sure, but chances are we can’t go out the way we came, and no one knows exactly where we are, so we shouldn’t count on rescue. That leaves one option: down the river.”

“Oh, you mean down the river that killed one of Kholkov’s men and sucked him into limbo? That river?”

“It goes somewhere. That tunnel is a good fifteen feet in diameter and the water’s moving fast and steady. If it narrowed anywhere down the line we’d see backflow or signs of a higher tide line on the walls. Believe me, it dumps out somewhere—either aboveground in a lake or pond, or into another sea cave.”

“And you’re sure about this?”

“Reasonably.”

“There’s a subjective judgment if I’ve ever heard one.” Remi chewed her lip for a moment. “What about this: You work your engineering magic with one of the tanks and blow a hole in the ceiling crack.”

“Not enough power, and we might bring the whole roof down on us.”

“True. Okay, we can wait for daylight then set the root tangle on fire. It’ll be a smoke signal—” She caught herself and frowned. “Scratch that. We’d asphyxiate long before help arrived.”

“You’ve done as much cave diving as I have,” Sam said. “You know the geology. That river’s our best chance. Our only chance.”

“Okay. One problem, though: Our escape pod is full of water and sitting fifteen feet below the surface.”

Sam nodded. “Yes, that’s a problem.”

After checking to make sure the main cavern was in fact sealed, they returned to the secondary cave and got to work, first retrieving their gear from the bottom, then scrounging through the Kriegsmarine crates for any odds and ends that might be of use. In addition to a well-stocked toolbox of mostly rusted tools they found four lanterns and a dozen stubby votivelike candles that lit at the first touch from Sam’s lighter. Soon the pier and surrounding water was dimly lit by flickering yellow light. While Remi sorted through their remaining gear and conducted an inventory of the toolbox, Sam stood at the edge of the pier, staring distantly into the water.

“Okay,” Remi said. “We’ve got two air tanks, one two-thirds full, a second completely full; two flashlights, both working, charge unknown; my camera’s shot but the binoculars are fine; the revolver is dry, but I can’t vouch for the bullets; two canteens of water and some slightly soggy beef jerky; a first-aid kit; your Gerber Nautilus multitool; one dry bag that’s in good shape, one that’s Swiss cheese; and, finally, two cell phones that are dry, working, almost fully charged, but useless inside here.”

“The motor?”

“I dried it out as best I could but we won’t know until we try it. As for the gas tank, I didn’t find any holes and all the valves are sealed, so I think it’s fine.”

Sam nodded and went back to staring at the water.

After ten minutes of this, he cleared his throat and said, “Okay, we can do it.” He walked over and sat down beside Remi.

“Let’s hear it,” she said.

He started explaining. When he was done, Remi pursed her lips, tilted her head, and then nodded. “Where do we start?”

It started with a tense, claustrophobic crawl for Sam. He had no trouble with either confined spaces or water, but had no love for the two combined.

Wearing only his mask and a dive belt, he first did a series of practice dives to expand his lung capacity, then spent a full minute on the surface doing deep-breathing exercises to oxygenate his blood to its maximum.