Nearing their third hour of travel, the sound of rushing water suddenly faded. The sub slowed and began spinning lazily.

“What’s happening?” Remi called.

“Not sure,” replied Sam.

He pressed his face to the dome and found himself staring up at a vaulted, stalactite-encrusted ceiling. He heard a scraping sound and looked left just in time to see a curtain of vines close over the dome like the swaying carpet arms inside an automated car wash. Sunlight burst through the dome, filling the interior with a yellow glow.

“Is that the sun?” Remi said.

“You bet it is!”

The hull scraped over sand, slowed, then came to a gentle halt. Sam peered ahead. They’d run aground in another lagoon.

“Remi, I think we have arrived.”

He unlatched the dome and swung it open. Cool, salt-tinged air rushed through the hatch. He draped his arms outside, letting them hang, then leaned his head back and let the sun wash over his face.

He heard something off to his left, opened his eyes, and turned his head. Sitting on the sand ten feet away were a young couple wearing dive fins and scuba harnesses. Mouths agape and frozen in place, they stared at Sam. The man had a farmer’s tan, the woman white-blond hair—Midwesterners on a tropical adventure.

“Good morning,” Sam said. “Doing a little cave diving, I see.”

The couple nodded in unison, saying nothing.

“Be careful you don’t get lost in there,” Sam offered. “It can be a little tricky getting back out. By the way, what year is it?”

“Leave the nice people alone, Sam,” Remi whispered from the back.

CHAPTER 21

Heaven,” Remi murmured. “Absolute heaven.”

True to his word, upon returning to their Four Seasons villa, Sam had, after they’d shared a long hot shower, ordered first a sumptuous lunch of seafood salad, hot sourdough bread, and a tropical fruit bowl, then a pair of masseuses, who’d spent an hour giving them a hot stone massage before moving to deep-tissue Swedish. Sam and Remi lay side by side on the veranda, the sheer curtains billowing around them in a light tropical breeze. Down the beach, the breakers gently washed in and out, nature’s own lullaby.

Sam, hovering on the edge of sleep, simply muttered, “This is living.”

The surprised couple they’d encountered upon their exit from the cave had in fact been Midwesterners—Mike and Sarah, from Minnesota and on their honeymoon. After three tries, they’d answered Sam’s “Where are we?” question: on Rum Cay’s northern coast between Junkanoo Rock and Liberty Rock. They had, by Sam’s calculation, traveled some nine miles along the underground river.

Mike and Sarah had graciously offered to give them a ride—and a tow to the mini sub, to which Sam had grown quite attached—down the coast in their rented boat. Forty-two hours after first touching down at Rum Cay, Sam and Remi were back at their landing beach. Their host, the mysterious beachcomber, was nowhere to be seen, so they muscled the sub into the undergrowth and left a note on the hut’s wall: Please keep an eye on this. We’ll be back for it. Sam had no idea exactly what he had planned, but it seemed wrong to simply abandon it.

They then climbed aboard the Bonanza and headed for the main island and their hotel.

Massages complete, Sam and Remi lay still for a while, dozing, then got up and went back inside. Having already given Selma a “We’re okay” text message, Sam now called her and put her on speakerphone. He gave her a quick rundown of their cave odyssey.

“Well, no one can accuse the Fargos of taking mundane vacations,” Selma replied. “I may have an answer to one mystery—why it was Kholkov who came after you. Rube called: Grigoriy Arkhipov was found dead in a Yalta parking lot; his hands and feet were missing. Amputation by shotgun. Rube told me to—”

“Tell us to be careful,” Sam finished. “We are.”

“The question is, how did Kholkov find you?”

“We’ve been wondering that ourselves. Did you check our—”

“No credit checks on the account you used, and all our computers here are firewalled, so I doubt they got your itinerary that way. Same with your passport records; the government is tight with those.”

Remi said, “That leaves airlines or . . .”

“Some lead they have that we don’t,” Sam finished. “But that begs the question, why hadn’t they already raided the caves?”

“I’ll keep working on it,” Selma said, “but I don’t think it came from our end.”

“Until we know, we’ll assume the worst and keep looking over our shoulders,” Remi said.

“Good. So, about this submarine . . .”

“The UM-77,” Sam offered.

“Right. You want me to get it back here?”

“We’d better,” Remi replied, “or Sam is going to pout.”

“It’s a piece of history,” he grumbled.

They’d agreed that once this was all over they would tell both the German and the Bahamian governments about the sub pens and let the two sort it out among themselves.

“And if no one wants it?” Remi had asked.

“We’ll put it above our mantel.”

Remi had groaned. “That’s what I was afraid of.”

Now, on the phone, Selma said, “I’ll work it out. Might take a few days, but I’ll get it back here. So: Kholkov got the bottle.”

“Afraid so. Any news for us?”

“Yes, in fact, a few things I think you’ll find interesting. Care to guess what else, besides the spitting beetle, is found only in the Tuscan Archipelago?”

Remi answered first. “Our black rose.”

“Right again. We’ll have to fill in the timeline, but it seems likely the ink was applied to the labels during Napoleon’s stay on Elba.”

“Or afterward with ink from there,” Sam added. “Either way, it’s another piece in the puzzle.”

“Well, here’s another one,” Selma said. “Our bottle appears to be something of an onion wrapped in a riddle. The leather label is not one piece, but two layers pressed together. I managed to peel away the top layer without causing any damage.”

“And?”

“There’s no ink present, but more etchings—a grid of symbols, eight across and four down for a total of thirty-two.”

“What kind of symbols?”

“You name it. Everything from alchemy to Cyrillic to astrology and everything in between. My guess: They’re customized shape codes with no connection to their origin. Sam, you’re probably familiar with shape code.”

He was. During his training at the CIA’s Camp Perry, they’d spent three days on cryptographic history. “It’s essentially a substitution cipher,” he explained to Remi. He grabbed a pad and pen from the nightstand and quickly sketched three symbols:

Sam said, “Now suppose the first symbol represents the letter c; the second, a; the third, t.”

“Cat,” Remi said. “Seems pretty simplistic.”

“It is, in a sense, but in another sense it’s a virtually unbreakable code. The military uses a version of it, something called a one-time pad. The theory is this: Two people have an encoding/decoding book. One sends a message using shape codes, the other deciphers it by substituting letters for shapes. Without a book, all you’ve got is random symbols. To anyone else, they’re meaningless.”

“And we don’t have a book,” Remi said.

“Nope. Selma, can you send us—”

“On the way as we speak. It’s not the original picture I took of the label, but Wendy used a vector drawing program to re-create some of the symbols. This’ll be just a sample.”

A moment later Sam’s e-mail beeped and he called up the image: