A London bus overtook him. As it churned slowly past, Massoudi peered through the fogged windows and saw a dozen tired-looking faces, nearly all of them black or brown. The new Londoners, he thought, and for a moment the professor of global governance and social theory wrestled with the implications of this. How many secretly sympathized with his cause? How many would sign on the dotted line if he laid before them a contract of death?

In the wake of the bus, on the opposite pavement, was a single pedestrian: oilskin raincoat, stubby ponytail, two straight lines for eyebrows. Massoudi recognized him instantly. The young man had been at the conference-same row as Hamida but on the opposite side of the auditorium. He’d been sitting in the same seat earlier that morning, when Massoudi had been the lone dissenting voice during a panel discussion on the virtue of barring Israeli academics from European shores.

Massoudi lowered his gaze and kept walking, while his left hand went involuntarily to the shoulder strap of his briefcase. Was he being followed? If so, by whom? MI5 was the most likely explanation. The most likely, he reminded himself, but not the only one. Perhaps the German BND had followed him to London from Bremen. Or perhaps he was under CIA surveillance.

But it was the fourth possibility that made Massoudi’s heart bang suddenly against his rib cage. What if the man was not English, or German, or American at all? What if he worked for an intelligence service that showed little compunction about liquidating its enemies, even on the streets of foreign capitals. An intelligence service with a history of using women as bait. He thought of what Hamida had said to him that afternoon.

“I grew up in Toronto, mostly.”

“And before that?”

“ Amman when I was very young. Then a year in Hamburg. I’m a Palestinian, Professor. My home is a suitcase.”

Massoudi made a sudden turn off Woburn Place, into the tangle of side streets of St. Pancras. After a few paces he slowed and looked over his shoulder. The man in the oilskin coat had crossed the street and was following after him.

HE QUICKENED his pace, made a series of turns, left and right. Here a row of mews houses, here a block of flats, here an empty square littered with dead leaves. Massoudi saw little of it. He was trying to keep his orientation. He knew London ’s main thoroughfares well enough, but the backstreets were a mystery to him. He threw all tradecraft to the wind and made regular glances over his shoulder. Each glance seemed to find the man a pace or two closer.

He came to an intersection, looked left, and saw traffic rushing along the Euston Road. On the opposite side, he knew, lay King’s Cross and St. Pancras stations. He turned in that direction, then, a few seconds later, glanced over his shoulder. The man had rounded the corner and was coming after him.

He began to run. He had never been much of an athlete, and years of academic pursuits had robbed his body of fitness. The weight of the laptop computer in his briefcase was like an anchor. With each stride the case banged against his hip. He secured it with his elbow and held the strap with his other hand, but this gave his stride an awkward galloping rhythm that slowed him even more. He considered jettisoning it but clung to it instead. In the wrong hands the laptop was a treasure trove of information. Personnel, surveillance photographs, communications links, bank accounts…

He stumbled to a stop at the Euston Road. Glancing over his shoulder, he saw his pursuer still plodding methodically toward him, hands in his pockets, eyes down. He looked to his left, saw empty asphalt, and stepped off the curb.

The groan of the lorry horn was the last sound Ali Massoudi ever heard. At impact the briefcase broke free of him. It took flight, turned over several times as it hovered above the road, then landed on the street with a solid thud. The man in the oilskin raincoat barely had to break stride as he bent down and snared it by the strap. He slipped it neatly over his shoulder, crossed the Euston Road, and followed the evening commuters into King’s Cross.

THE BRIEFCASE HAD REACHED Paris by dawn, and by eleven it was being carried into an anonymous-looking office block on King Saul Boulevard in Tel Aviv. There the professor’s personal effects were hastily inspected, while the hard drive of his laptop computer was subjected to a sustained assault by a team of technical wizards. By three that afternoon the first packet of intelligence had been forwarded to the Prime Minister’s Office in Jerusalem, and by five a manila file folder containing the most alarming material was in the back of an armored Peugeot limousine heading toward Narkiss Street, a quiet leafy lane not far from the Ben Yehuda Mall.

The car stopped in front of the small apartment house at Number 16. Ari Shamron, the twice former chief of the Israeli secret service, now special adviser to the prime minister on all matters dealing with security and intelligence, emerged from the backseat. Rami, the black-eyed chief of his personal security detail, moved silently at his heels. Shamron had made countless enemies during his long and turbulent career, and because of Israel ’s tangled demographics, many were uncomfortably close. Shamron, even when he was inside his fortresslike villa in Tiberias, was surrounded always by bodyguards.

He paused for a moment on the garden walkway and looked up. It was a dowdy little building of Jerusalem limestone, three floors in height, with a large eucalyptus tree in front that cast a pleasant shadow over the front balconies. The limbs of the tree were swaying in the first cool wind of autumn, and from the open window on the third floor came the sharp odor of paint thinner.

Shamron, as he entered the foyer, glanced at the mailbox for apartment number three and saw it was absent a nameplate. He mounted the stairs and tramped slowly upward. He was short of stature and was dressed, as usual, in khaki trousers and a scuffed leather jacket with a tear in the right breast. His face was full of cracks and fissures, and his remaining fringe of gray hair was cropped so short as to be nearly invisible. His hands were leathery and liver-spotted and seemed to have been borrowed from a man twice his size. In one was the file.

The door was ajar when he arrived on the third-floor landing. He placed his fingers against it and gently pushed. The flat he entered had once been meticulously decorated by a beautiful Italian-Jewish woman of impeccable taste. Now the furniture, like the beautiful Italian woman, was gone, and the flat had been turned into an artist’s studio. Not an artist, Shamron had to remind himself. Gabriel Allon was a restorer-one of the three or four most sought-after restorers in the world. He was standing now before an enormous canvas depicting a man surrounded by large predatory cats. Shamron settled himself quietly on a paint-smudged stool and watched him work for a few moments. He had always been mystified by Gabriel’s ability to imitate the brushstrokes of the Old Masters. To Shamron it was something of a parlor trick, just another of Gabriel’s gifts to be utilized, like his languages or his ability to get a Beretta off his hip and into firing position in the time it takes most men to clap their hands.

“It certainly looks better than when it first arrived,” Shamron said, “but I still don’t know why anyone would want to hang it in his home.”

“It won’t end up in a private home,” Gabriel said, his brush to the canvas. “This is a museum piece.”

“Who painted it?” Shamron asked abruptly, as though inquiring about the perpetrator of a bombing.