“No one’s immune to beauty,” Sam replied. “Even him, it seems.”

The question was, Sam and Remi knew, aside from the scenery, why exactly were they here?

Though they had deciphered only the first part of the latest riddle, they’d felt confident enough in their solution to immediately call Selma and ask her to arrange passage from Monaco to Bavaria. By midmorning, having thanked Yvette for her hospitality and promised to return and recount their exploration, they were on their way to the Nice airport, from there to Paris, and then to Salzburg, where they rented a car and drove the remaining thirty miles to Schönau am Königssee.

“What time does our boat leave in the morning?” Remi asked.

“Nine. Remind me to check the weather tonight.” Even now in late spring the Königssee valley’s weather was volatile, prone to days that could go from warm sunshine to brooding clouds to snow in the space of an hour. The savvy Königssee visitor was always armed with a spare sweater or Windbreaker.

Given Saint Bartholomae’s location, there were only two ways to reach it, either by boat from Schönau or by hiking in through the surrounding mountain passes. While the latter option piqued their wanderlust they knew it would have to wait for their next visit. Time was not their friend now. While their infiltration of Bondaruk’s estate had put them a step ahead, given how long the man had likely been pursuing the Lost Cellar, and given the scope of his resources, their lead could be short-lived. They’d seen no sign of Kholkov or his men, but still a touch of paranoia seemed warranted. Until they found whatever secrets Saint Bartholomae’s held and were safely away, they’d assume they were being watched. Moreover, they would assume their invasion of Khotyn had enraged an already frustrated Bondaruk. Whatever restraint the man might have thus far shown was probably gone. What they couldn’t predict was, given the lengths to which Bondaruk had already gone, what might he do now?

If the Königssee was the height of alpine beauty, Sam and Remi decided the nearest village, Schönau, epitomized the word “quaint.”

Home to five thousand souls, Schönau, which sat astride the stone-strewn river that fed the Königssee, was a sprawling collection of homes and businesses, each one a Bavarian architectural gem that seemed more chalet than building. On the eastern side of Schönau’s truncated S-shaped harbor, just south of a string of cafés, restaurants, and hotels, sat a curved line of boathouses whose styling seemed torn from the pages of a Vermont covered bridges coffee-table book.

Now, as Sam steered their car down the tree-lined road to Schönau, they could see the day’s last tour boats gliding in and out of the boathouses, their wakes forming translucent fans atop the emerald water.

A few minutes later they pulled into the parking lot of the Hotel Schiffmeister. Fronted by white and red awnings and balconies bursting with red and white and pink flowers, the Schiffmeister’s facade was painted in earth-toned rococo traceries of intertwined flowers and vines and spirals. As the valet saw to their car and the bellhop to their bags, they walked into the lobby and found the front desk. Minutes later they were being shown into their lakefront suite.

They each showered, wrapped themselves in the hotel’s heavy terry cloth robes, then ordered coffee from room service and settled on the balcony overlooking the water. With the sun falling behind the mountains to the west, the lake was backlit in a golden hue and the calm evening air was growing chilled. On the streets and sidewalks below, tourists strolled along, looking in shop windows and taking pictures of the harbor.

Sam powered up his iPhone and tapped into the hotel’s satellite Internet connection. “Something from Selma,” he said, scanning their e-mail. With typical efficiency she had compiled a report on Xerxes I and the Achaemenid Dynasty, one a condensed version, the other more detailed. Sam forwarded both to Remi’s iPhone and they spent the next thirty minutes learning about the ancient Persian king.

The eighth attested ruler of the Achaemenid Dynasty, Xerxes I took the throne at the age of thirty-five and wasted no time living up to his warlike reputation, first crushing a revolt in Egypt, then in Babylon, where he declared the Babylonian Empire abolished and promptly spirited away the golden idol of Bel-Marduk and had it melted down, effectively crushing the empire’s spiritual foundations.

Two years later Xerxes turned his wrath on the Athenians, who had fallen afoul of the Achaemenid Dynasty at the Battle of Marathon, where they’d thwarted King Darius I’s attempt to conquer all of Greece.

In 483 B.C. Xerxes began preparations for the invasion of Greece in dramatic fashion by creating a bridge to span the Hellespont, then by digging a navigable canal across the Athos Isthmus.

From Sardis, Xerxes and his army bulldozed north through Thrace and Macedonia before being stalled at Thermopylae by King Leonidas and his Spartans, who despite a valiant effort were killed to a man. Now unhindered, Xerxes continued south down the coast to Athens, where he plundered the abandoned city. This would prove to be the zenith of Xerxes’ invasion; shortly thereafter he lost much of his fleet at the Battle of Salamis, then most of his land force at the Battles of Plataea and Mycale in 479 B.C.

Leaving the army in the hands of one of his generals, Mardonius, Xerxes retired to Persepolis, in modern-day Iran, where he spent the remainder of his days dealing with political turmoil. He was eventually murdered by the captain of his guard, possibly at the behest of his own son, Artaxerxes I, who took the Achaemenid throne in 464 B.C.

“Oh, what a tangled web,” Remi said as she finished. Sam, ten seconds behind her, looked up and replied, “Not a nice guy, Mr. Xerxes.”

Remi smiled. “Are any of them?”

“Not often. Well, if we’re looking to Xerxes’ biography for clues about what Bondaruk’s after, the first thing that strikes me is the Bel-Marduk idol from Babylon, but history says it was melted down.”

“What if the history is wrong? What if he melted down a copy, made off with the original, then lost it somewhere?”

“Could be.” Sam typed up a quick e-mail to Selma and sent it off. He got a “Checking on it” e-mail a few minutes later. “Okay, other possibilities?”

“It seems everything went downhill for Xerxes after his invasion of Greece. He surrendered control of the army, went home, loitered about for a few years, then was assassinated. Maybe he lost something on the campaign that in his own mind cursed his reign.”

“And Bondaruk thinks recovering it will somehow balance the scales,” Sam finished. “Put things right for the Xerxes line.”

“As you said, the safe money is on Bel-Marduk, but history treats the Babylonian uprising as nothing more than an annoyance for Xerxes.”

“How about the Egyptian revolt? It was roughly the same time.”

Remi sighed. “It’s possible. The problem with history—especially ancient history—is that often only the highlights get the attention. For all we know, buried in an ancient text in some library or museum vault there’s a list of treasures stolen by Xerxes, along with their disposition.”

“Great,” Sam said with a smile. “Where do we start?”

“Take your pick: Cairo, Luxor, Istanbul, Tehran. . . . If we start digging today we’ll be done in ten or twelve years.”

“Not the best course, then. Okay, let’s see if we can narrow things down: Xerxes ruled for twenty years. In that time he embarked on three major campaigns: Egypt, Babylon, and Greece. Of the three, Greece was the most important and, arguably, a turning point for his reign. Why don’t we focus on the Greco-Persian war and see where that takes us?”