He placed his hand on the wall. “There must be a source of water somewhere behind here.”

“Like a cave.”

“Maybe.”

Bukolov frowned. “But this wall is clearly not De Klerk’s waterfall.”

“No. But there is a water source close by here.” He patted his dog’s side. “Good boy, Kane.”

The shepherd resisted his praise. He sniffed at Tucker’s sandy fingertips, barked three times rapidly, then jumped back on the wall.

“Shh!” Tucker said.

Kane obeyed, going silent, but he stayed with his forepaws braced on the rock face, his nose pointed up.

What are you trying to tell me?

Tucker backed away from the cliff face, shaded his eyes with a hand, and looked up.

From behind them, Christopher called, “What’s happening?”

Anya was with him. “Our canyon came to a dead end. Then we heard the barking.”

As they closed the distance, Christopher clearly hobbled on his left leg. “Twisted my ankle on some loose shale,” he explained. “Hurts but I’m fine.”

Anya stared over at Kane. “What’s he found?”

“I don’t—”

Then he understood.

Craning his neck, he continued down the ravine. He soon discovered what he was looking for: a jumble of boulders piled against the left side of the gorge.

“I should be able to climb that.”

“Why? What the devil is going on?” Bukolov asked, dragging everyone with him.

Tucker faced them. “I’m climbing up. Something on top of the plateau has Kane all hot and bothered.”

“Then I’m coming, too,” Anya said.

He eyed her cast.

“I can manage. If I could climb to the top of Klipkoppie fort, I can scale this.”

Christopher hung back, plainly compromised by his leg.

“Stay with Doctor Bukolov,” Tucker instructed him. “We’ll scout it out first.”

Not knowing what was up there, Tucker wanted an extra set of eyes and ears. Bending down, he hauled Kane over his shoulders in a fireman’s carry and started up the steps. It was a precarious climb in spots, but they reached the top.

Boulders littered the summit, a veritable broken maze. They had succeeded in mounting the section of cliff between the two tusk-shaped canyons. To their right, the plateau ended at the pig’s snout. To the left, a pair of higher plateaus abutted against this one, like the raised shoulders of a monstrous beast.

“We’re standing atop the Boar’s Head,” he realized aloud.

It had to be significant.

Tucker returned Kane to his feet with the instruction “SEEK.”

Without hesitation, the shepherd sprinted in the direction of the taller mesas, dodging around boulders. Tucker and Anya followed, and after a few twists and turns, they found Kane sitting beside a pool of water. On the far side, a sparkling cascade poured into it, flowing along a series of cataracts from the neighboring, higher lands.

His tail wagged happily, as if to say: This is what I was talking about.

“What on earth . . .” Anya whispered and stared at the dancing flow of water over rock. “Is that De Klerk’s waterfall? If so, where’s the cave?”

“I don’t know.”

Tucker took a moment to orient himself. Something was wrong with this picture. The pool next to Kane was kidney shaped, about twenty feet across. He stared at the stream flowing into it—as it likely had all season long. The pool seemed too tiny to capture all that flow.

So why hasn’t this pool overflowed by now?

Then he knew the answer.

36

March 21, 4:38 P.M.

Groot Karas Mountains, Namibia

Tucker knelt at the pool’s edge with Kane. With his head cocked to the side, he stared across the surface, watching the gentle ruffle of ripples spread outward from the cascade on the far side.

“What are you looking for?” Anya asked.

“There!” He pointed near the center of the pond, where the flow of ripples slightly churned in on themselves. “See that swirl.”

“Yes, I see it, but what does it mean?”

“It means the pool is draining into something beneath it. That’s why it’s not overflowing its banks as the waterfall continues to pour into it. It drains below as quickly as it fills above.”

A lilt of excitement entered Anya’s voice. “You’re thinking it might be draining into a cave.”

“Maybe the cave. We’re exactly at De Klerk’s coordinates here.”

Tucker crossed back to the edge of the cliff and called down to Christopher. “I need the climbing rope from my pack. Can you toss it up?”

“Just a minute!”

“What did you find?” Bukolov yelled to them.

“That’s what I’m about to find out!” he hollered down.

Christopher pulled out the nylon climbing rope, tied a monkey’s fist in one end, and hurled the end up to Tucker. He caught it on the first try and reeled the rest of the length up. Before returning to the pond, he knotted the rope around one of the poolside boulders.

Pulling on gloves, he stepped back to the waterline and flung the other end of the rope—the one with the monkey’s fist still tied in it—out toward the center of the pool.

The knotted end sank—then after a few tense breaths, the remaining line between his fingers began uncoiling, snaking into the water. Slowly at first, then faster and faster. With a twang, the last of the line sprang taut in his fingertips, forming a straight line from the boulder to the whirlpool.

Tucker waded out a few feet, sliding his palm along the rope. When he was thigh deep, he felt a slight tidal pull of the drainage vortex. His fingers tightened on the line. He moved step by step. The tug on his legs became stronger. By the time he was waist-deep, his boots began to slide on the slippery rocks underfoot.

For safety’s sake, he straddled the rope, grasped it with both hands, and began backing toward the center.

Step by cautious step.

Then his left foot plunged into nothingness. Gasping in surprise, he dropped to his right knee. Water foamed and roiled around his upper chest.

“Tucker! Careful.” Anya stood on the bank, a worried hand at her throat.

Kane barked at him.

“I’m okay,” he told them both.

He pulled on the rope and yanked his left foot back from the hole. He gained a firmer stance against the tide. With his right hand clutching the rope, he bent down and reached back with his left. He probed the pool’s bottom until his fingers touched the rim of the hole.

“Seems wide enough,” he called to Anya.

“Wide enough for what?”

“Me.”

“Tucker, no. You don’t know what’s down there. Don’t—”

He took a deep breath, sat down on his butt, slid both feet into the hole, and lowered himself downward.

The current of the vortex grabbed him hard and sucked him through the drain. His gloved fingers slid along the rope in fits and starts. Then he popped out of the flooded chute and found himself swinging in open air.

He dangled and twisted in the faucet of water pouring down from the ceiling of stone overhead. Watery light flowed down with it, but not enough to illuminate the cavernous space below him.

Spinning on the line, he lowered himself hand over hand.

Finally his boots touched solid ground. He found his footing, backed up a few steps out of the torrential stream, and let go of the rope. Bent double, gasping, he spit water, coughed, and wiped clear his eyes.

He finally straightened, expecting to see nothing but what little daylight filtered through the chute above, but as his eyes adjusted, he noted fiery slivers of sunlight shining around him—some four or five of them, coming through fissures in the roof or sloping walls.

Still, they offered scant illumination.

He plucked his flashlight out of a buttoned pocket and panned it around the roughly oval-shaped cavern. The waterfall, which marked the space’s center point, flooded across the bottom of the cave, pooling in some places but mostly draining through fissures in the floor.