He stuffed the specimen bag into his shorts. This was one prize he would keep very close to himself. He toweled the water from his hair, sat on the edge, and looked down, hoping to see the shark. Keep coming up for me, he thought, and I’ll put a damn bullet in your primeval head.

For a split second, he believed he could see it in the deep water below him, but then it faded and he guessed it had given up the chase.

He tossed away the towel, then eased back the throttle, prepared for a nice, leisurely cruise back to the shore. The boat belly-whapped on the choppy water, sending a cool spray shooting back at him. Feeling relaxed and satisfied, he brought out a silver metal box from under the foredeck hold, popped open the latches, and removed his sat phone. After turning it on, he said, “Frikkie.”

The phone dialed automatically. He could hear the whirring ring: once, twice. Come on, he thought. You have to be there. This is what you’ve been waiting for.

“Yes?”

“I got it.”

“Good. Correct that.Great . Take care with it.”

Blaine smiled. “It’s as safe as my family jewels, Frik. I tell you, though, it is a strange-looking thing. I do hope it was worth that beautiful woman’s life.”

“Wait! What did you just say?”

“Peta. I thought it might be tidier if she didn’t surface to ask questions. Seemed like a nice place to leave someone buried. She and Simon kind of disap—”

“Go! The hell! Back! Now!”

“What?”

Even as Blaine spoke, he started cutting the wheel of the boat, turning around. It rocked as its own wake hit it from behind, and for a moment the propellers cut at air. Then he gunned the throttle.

“Are you going back?”

“On my way. Now tell me—”

“You idiot. Did I tell you to kill her?”

“No, Frikkie, but it seemed like a…how you say…no-brainer. Why would you—”

“Because she still has a piece of the artifact, you fool!”

The Venezuelan let that sink in. This was not good. People rarely screwed up on Frikkie more than once. They didn’t live that long.

“You’d better hope to God she’s still alive down there, Blaine. And if she isn’t, you’d be better off not coming up again yourself.”

He didn’t respond. He could only think that it had been a long time since he’d left her in the cave. The best chance that she was alive was if she was somehow able to breathe the free-flowing gases from her tanks. Slim possibility of that, but a possibility nonetheless.

“Are you at the rig yet?”

“In thirty seconds, Frikkie. I’ll go down. I’ll see.”

“She’d better be alive, Blaine. You hear me?”

“I hear you.”

Blaine shut off the call and, one hand holding the wheel, grabbed his fins and suited up again.

Peta saw the precious mixture gushing out of the cut hoses like streams of water from the mouth of a crazed snake.

If something like this happened during a rec dive, she could just hold the free-flowing hose up to her mouth and breathe while she ascended. This deep, though, that wouldn’t work. With the air shooting out so fast, there was no way it would last long enough for her to get out of the cave, even if shecould sip the air like that.

Her second option was drowning. Already, she was feeling a little glow in her chest, the beginning of that amazing reflex that would eventually demand that she open her mouth and breathe, no matter what was touching her lips. She would suck in the water, putting an end to that crazed demand.

In minutes she’d be dead.

Then she realized that the answer was right in front of her: Simon. His tanks were intact and still had plenty of air in them. If she could hold her breath a little longer, she might be able to get to them.

Trying to avoid looking at the bulging eyes and the rubbery, puffed-out lips, she reached for the regulator. You’re saving my life, Simon, she thought as she took a breath. For a moment she wondered if it had been a regulator failure that had killed him, but the mechanism worked fine. She took a few even breaths before she slid off her own BC vest and tanks, and watched them float to the top of the cave. With Simon’s mouthpiece locked between her teeth, she reached around him and undid the buckle and the Velcro of his BC. As she pulled it open, she tried to slide it down, but his arms wouldn’t cooperate.

Take your time, she told herself. You have to be patient. Don’t expend too much energy.

As gently as she could, she pushed his right arm out of the vest. It wasn’t easy. The arm felt stiff, too long for the armhole. She had to wedge Simon’s body against the wall and use all her strength to force it through.

With one arm out, the other became much simpler.

Once she had the tanks free, she turned away from her friend’s body and ended up facing the wall mural. Something in the shapes drew her attention, as if there were a secret there that she would understand if she just stared at it long enough. Was that shape a head? No, not a head. More like something from a microbiology class—as if the mural were some grotesque enlargement of a slide.

Several sharp beeps drew her attention away from the images. She looked around, afraid that someone else might be attacking, and realized that the sound was coming from Simon’s dive watch.

Time to get out of here, she thought. She had to let the regulator slip from her mouth as she slid her arms into Simon’s considerably larger vest. Putting the mechanism back in her mouth, she took another slow, steady breath. She had to stay calm, not breathe too fast.

It occurred to her that she wasn’t entirely sure what she’d find when she did escape this cave. Would Blaine be waiting in his boat to see if she made it out? What about Simon’s pilot? What would she do if there was no boat up there waiting for her?

None of those questions had answers now. She had to keep her focus. The first task was to get out of this cavern and back to the surface.

She looked ahead to the cave opening, then around at the other walls, their surfaces as smooth as glass. What this place was, she had no idea. She did know that if she stayed here much longer looking for the answer, she wouldn’t live to tell anyone.

She took one last look around the domelike cave. About to turn away, she spotted something she hadn’t noticed earlier: a hole, low to the ground on the other side of the cave. Another way out, perhaps. A good thing, given that she didn’t know what Blaine might have left for her on the path they’d used to come in.

Swimming over to the second passage, she got her head down low to shoot her light inside. The dim light didn’t reveal much. She hesitated for a moment, and went in.

This channel was much narrower, barely large enough for her body and tanks. The walls were even smoother than in the first cavern, glassine and iridescent, silky to the touch.

Half a dozen feet in, the tube opened into a small chamber, a circular passageway with three other thin tubes shooting off in different directions. The chamber was big enough for her to kneel and look around.

On the wall behind her, she saw what looked like a shape. While she watched, it seemed to move—a dark blue-black shimmer. Tiny plankton floating in the water gave the shape a hazy, blurry outline, and she guessed that the apparent motion was a result of the light reflecting on the strange surface, like the inside of the shell of an oyster. The image of an oyster reminded her of the strangest aspect of this cavern: there should have been fish and crustaceans making this nice deep-water pocket home, but she saw nothing alive. Nothing at all.

She heard a series of high-pitched beeps. Her own dive watch this time. She looked at the maze of other channels ahead leading to other chambers, other secrets. They might lead to another way out, but she didn’t have time for errors. She would have to leave the way she’d come in.