As the carriage sunk toward the lobby, Zoe examined her reflection in the stainless steel doors. You were left on our doorstep by Gypsies, her mother used to say. It seemed the only possible explanation for how a child of Anglo-Saxon heritage had come into the world with black hair, dark brown eyes, and olive-complected skin. As a young girl, Zoe had been self-conscious about her appearance. But by the time she went up to Cambridge, she knew it was an asset. Zoe's looks made her stand out from the crowd, as did her obvious intelligence and biting sense of humor. Jason had been smitten the first time she walked into his office. He'd hired her on the spot and expedited her ascent up the ladder of success. In moments of honesty, Zoe admitted that her career had been helped by her looks. But she was also smarter than most of her colleagues. And no one in the newsroom worked harder.

As the elevator doors opened, she spotted a knot of reporters and editors gathered in the lobby, debating a proper setting for that evening's drinking session. Zoe slipped past with a polite smile—she had acquaintances on the staff but no true friends—and stepped into the street. As usual, she headed across the Thames to the Cannon Street Underground Station. Had home been her true destination, she would have taken a westbound Circle Line train to Embankment and transferred to a Northern Line train to Hampstead. Instead, she stepped onto an eastbound train and rode it as far as St. Pancras Station, the new London terminal for high-speed Eurostar trains.

Tucked into the outside flap of Zoe's briefcase was a ticket for the 7:09 train to Paris. She purchased several magazines before clearing passport control, then made her way to the departure platform, where the boarding process was already under way. She found her seat in the first-class cabin and in short order was presented with a rather good glass of champagne. A trashy book. A couple of DVDs. Maybe a walk in Hampstead Heath if it's not raining...Not quite. She peered out the window as the train eased from the station and saw an attractive dark-haired woman gazing back at her. This is the last time, Gypsy girl, she thought. This is the very last time.

Few people noticed Eli Lavon's arrival in Amsterdam the following day, and those who did mistook him for someone else. It was his special talent. Regarded as the finest street surveillance artist the Office had ever produced, Lavon was a ghost of a man who possessed a chameleon-like ability to change his appearance. His greatest asset was his natural anonymity. On the surface, he appeared to be one of life's downtrodden. In reality, he was a natural predator who could follow a highly trained intelligence officer or hardened terrorist down any street in the world without attracting even a flicker of interest. Ari Shamron liked to say that Lavon could disappear while shaking your hand. It was not far from the truth.

It was Shamron himself, in September 1972, who introduced Lavon to a promising young artist named Gabriel Allon. Though they did not realize it then, both had been selected to take part in what would become one of the most celebrated and controversial missions ever undertaken by Israeli intelligence—Wrath of God, the secret operation to hunt down and assassinate the perpetrators of the Munich Olympics massacre. In the Hebrew-based lexicon of the team, Lavon was an ayin, a tracker and surveillance specialist. Gabriel was an aleph. Armed with a .22 caliber Beretta pistol, he personally assassinated six of the Black September terrorists responsible for Munich. Under Shamron's unrelenting pressure, they stalked their prey across Western Europe for three years, killing both at night and in broad daylight, living in fear that at any moment they would be arrested and charged as murderers. When they finally returned home, Gabriel's temples were the color of ash, his face that of a man twenty years his senior. Eli Lavon, who had been exposed to the terrorists for long periods of time with no backup, suffered innumerable stress disorders, including a notoriously fickle stomach that troubled him to this day.

When the Wrath of God unit was formally disbanded, neither Gabriel nor Lavon wanted anything more to do with intelligence work or killing. Gabriel took refuge in Venice to heal paintings while Lavon fled to Vienna, where he opened a small investigative bureau called Wartime Claims and Inquiries. Operating on a shoestring budget, he managed to track down millions of dollars' worth of looted Holocaust assets and played a significant role in prying a multibillion-dollar settlement from the banks of Switzerland. Lavon's activities earned him few friends, and in 2003 a bomb exploded inside his office, seriously wounding him and killing two of his employees. Lavon never attempted to rebuild in Vienna, choosing instead to return to Israel and pursue his first love, archaeology. He now served as an adjunct professor at Hebrew University and regularly took part in digs around the country. And twice a year he returned to the Office academy to lecture the new recruits on the fine art of physical surveillance. Invariably, one would ask Lavon about his work with the legendary assassin Gabriel Allon. Lavon's response never varied: "Gabriel who?"

By training and temperament, Lavon was prone to handle delicate objects with care. That was especially true of the single sheet of paper he accepted in the sitting room of a suite at the Ambassade Hotel. He examined it for several moments in the half-light before placing it on the coffee table and peering curiously at Gabriel and Chiara over his gold half-moon reading glasses.

"I thought you two were hiding out from Shamron in the deepest corner of Cornwall. How in the world did you get this?"

"Is it real?" asked Gabriel.

"Absolutely. But where did it come from?"

Gabriel gave Lavon an account of the investigation thus far, beginning with Julian Isherwood's unannounced appearance on the cliffs of Lizard Point and ending with the story of Lena Herzfeld. Lavon listened intently, his brown eyes darting back and forth between Gabriel and Chiara. At the conclusion, he studied the document again and shook his head slowly.

"What's wrong, Eli?"

"I've spent years searching for something like this. Leave it to you to stumble on it by accident."

"Something like what, Eli?"

"Proof of his guilt. Oh, I found scraps of corroborating evidence scattered across the graveyards of Europe, but nothing as damning as this."

"You recognize the name?"

"Kurt Voss?" Lavon nodded his head slowly. "You might say that SS-Hauptsturmfuhrer Kurt Voss and I are old friends."

"And the signature?"

"To me, it's as recognizable as Rembrandt's." Lavon glanced down at the document. "Whether you ever manage to find Julian's painting, you've already made a major discovery. And it needs to be preserved."

"I'd be more than happy to entrust it to your capable hands, Eli."

"I assume there's a price involved."

"A small one," said Gabriel.

"What's that?"

"Tell me about Voss."

"It would be my distinct displeasure. But order us some coffee, Gabriel. I'm a bit like Shamron. I can't tell a story without coffee."