Lavon switched on a small Maglite and led the way into the sitting room. The furnishings were of flea market quality, the floor was cracked linoleum, and the walls were bare except for a single travel poster depicting the Dome of the Rock in Jerusalem. Gabriel walked over to the long trestle table that served as Samir’s desk. It was empty except for a single yellow legal pad and a cheap desk lamp.

He switched on the lamp and examined the pad. Two-thirds of it had been used and the top page was blank. He moved his fingers over the surface and felt impressions. An amateur’s mistake. He handed the pad to Lavon, then took hold of the flashlight and shone it at an angle over the surface of the table. It was covered in a fine layer of dust except for a precise square in the center-the spot, Gabriel reckoned, where Samir’s computer had been before his flight from Amsterdam.

“Search the furniture cushions,” Gabriel said. “I’ll have a look around the rest of the flat.”

He went through a doorway into the kitchen. The debris of Samir’s final gathering with his acolytes from the al-Hijrah Mosque lay strewn across the linoleum countertops: empty takeaway containers, greasy paper plates, discarded plastic utensils, squashed teabags. Gabriel opened the refrigerator, a favorite terrorist storage space for explosives, and saw that it was empty. The same was true of all the cabinets. He looked in the cupboard beneath the sink and found nothing but an unopened container of kitchen cleaner. Samir, Islamic theoretician and spokesman for the jihadi cause, was a typical bachelor slob.

Gabriel paused for a moment in the sitting room to check on Lavon’s progress, then headed down a short hallway toward the back of the apartment. Samir’s bathroom was as appalling as the kitchen. Gabriel gave it a rapid search, then entered the bedroom. A stripped mattress lay slightly askew on the metal frame and the three drawers of the dresser were all partially open. Samir, it seemed, had packed in a hurry.

Gabriel removed the top drawer and dumped the remaining contents onto the bed. Threadbare underwear, mismatched socks, a book of matches from a discotheque in London ’s Leicester Square, an envelope from a photo-processing shop around the corner. Gabriel slipped the matches into his pocket, then opened the envelope and leafed through the prints. He saw Samir in Trafalgar Square and Samir with a member of the Queen’s Life Guard outside Buckingham Palace; Samir riding the Millennium Wheel and Samir outside the Houses of Parliament. The last photograph, Samir posing with four friends in front of the American embassy in Grosvenor Square, caused Gabriel’s heart to skip a beat.

Five minutes later he was walking calmly along the empty pavements of the Hudsonstraat, with the photographs in his pocket and Lavon at his side. “If the dates on the pictures are correct, it means Samir and his friends were in London four months ago,” he said. “Someone should probably go to London to have a word with our friends at MI5.”

“I can see where this is heading,” Lavon said. “You get to go to ride into London like a knight on a white horse and I get to go blind reading the rest of Solomon Rosner’s files.”

“At least you get to have your Thai food.”

“Why did you have to mention the Thai food?”

G abriel had spent much of his life eluding the police forces and security services of Europe, and so it was with considerable reluctance that he agreed to be met at Heathrow Airport the following afternoon by MI5.

He spotted the three-man reception team as he came into the arrivals hall. It was not difficult; they were wearing matching mackintosh raincoats, and one was holding Gabriel’s photograph. He had been instructed to let the MI5 men make the approach, so he went to the information kiosk and spent several minutes pretending to scrutinize a list of London hotels. Finally, anxious to deliver his briefing before the terrorists struck, he walked over and introduced himself. The officer with the photograph took him by the arm and led him outside to a waiting Jaguar limousine. Gabriel smiled. He had always harbored a secret envy of British spies and their cars.

The rear window slid down a few inches and a long, boney hand beckoned him over. The hand was attached to none other than Graham Seymour, MI5’s long-serving and highly regarded deputy director general. He was in his late fifties now and had aged like fine wine. His Savile Row pin-striped suit fit him to perfection, and his full head of blond hair had a silvery cast to it that gave him the look of those male models one sees in advertisements for costly but needless trinkets. As Gabriel climbed into the car, Seymour appraised him silently for a moment with a pair of granite-colored eyes. He did not look pleased, but then few men in his position would. The Netherlands, France, Germany, and Spain all had their fair share of Muslim radicals, but among intelligence professionals there was little disagreement over which country was the epicenter of European Islamic extremism. It was the country Graham Seymour was sworn to protect: the United Kingdom.

Gabriel knew that the crisis now facing Britain was many years in the making and, to a large degree, self-inflicted. For two decades, beginning in the 1980s and continuing even after the attacks of 9/11, British governments both Labour and Tory had thrown open their doors to the world’s most hardened holy warriors. Cast out by countries such as Egypt, Saudi Arabia, Jordan, and Syria, they had come to London, where they were free to publish, preach, organize, conspire, and raise money. As a result, Great Britain, the land of John Locke, William Shakespeare, and Winston Churchill, had unwittingly allowed itself to become the primary incubator of a violent ideology that sought to destroy everything for which it had once stood. The British security and intelligence services, confronted by a gathering storm, had responded by choosing the path of accommodation rather than resistance. Extremism was tolerated so long as it was directed outward , toward the secular Arab regimes, America, and, of course, Israel. The failure of this policy of appeasement had been held up for all the world to see on July 7, 2005, when three bombs exploded inside the London Underground and a fourth tore a London city bus to shreds in Russell Square. Fifty-two people were killed and seven hundred more wounded. The perpetrators of this bloodbath were not destitute Muslims from abroad but middle-class British boys who had turned on the country of their birth. And all evidence suggested it was only their opening salvo. Her Majesty’s security services estimated the number of terrorists residing in Britain at sixteen thousand-three thousand of whom had actually trained in al-Qaeda camps-and recent intelligence suggested that the United Kingdom had eclipsed America and Israel as al-Qaeda’s primary target.

“It’s funny,” said Seymour, “but when we checked the manifest for the flight from Amsterdam we didn’t see anyone on the list named Gabriel Allon.”

“Obviously you didn’t look hard enough.”

The MI5 man held out his hand.

“Let’s not do this, Graham. Haven’t we more pressing matters to deal with than the name on my passport?”

“Give it to me.”

Gabriel surrendered his passport and stared out the window at the traffic rushing along the A4. It was 3:30 in the afternoon and already dark. No wonder the Arabs turned to radicals when they moved here, he thought. Perhaps it was light deprivation that drove them to jihad and terror.

Graham Seymour opened the passport and recited the particulars. “Heinrich Kiever. Place of birth, Berlin.” He looked up at Gabriel. “East or West?”

“Herr Kiever is definitely a man of the West.”

“We had an agreement, Allon.”

“Yes, I know.”

“It stated that we would grant you absolution for your multitude of sins in exchange for a simple commitment on your part-that you would inform us when you were coming to our fair shores and that you would refrain from conducting operations on our soil without obtaining our permission and cooperation beforehand.”

“I’m sitting in the back of an MI5 limousine. How much more cooperation and notification do you require?”

“What about the passport?”

“It’s nice, isn’t it?”

“Do the Germans know you’re abusing their travel documents?”

“We abuse yours, too, Graham. It’s what we do.”

“We don’t do it. SIS makes a point of traveling only on British or Commonwealth passports.”

“How sporting of them,” Gabriel said. “But it’s far easier to travel the world on a British passport than it is on an Israeli one. Safer, too. Take a trip to Syria or Lebanon some time on an Israeli passport. It’s an experience you’ll never forget.”

“Smart-ass.” Seymour handed the passport to Gabriel. “What were you doing in Amsterdam?”

“Some personal business.”

“Elaborate, please.”

“I’m afraid I can’t.”

“Did the Dutch know you were there?”

“Not exactly.”

“I’ll take that as a no.”

“I always heard you were good, Graham.”

Seymour pulled his face into a fatigued frown, a sign that he’d had enough of the verbal sparring match. The inhospitality of his reception came as little surprise to Gabriel. The British services did not care much for the Office. They were Arabists by education, anti-Semites by breeding, and still resented the Jews for driving the Empire out of Palestine.

“What have you got for me, Gabriel?”

“I think an al-Qaeda cell from Amsterdam might have entered Britain in the last forty-eight hours with the intention of carrying out a major attack.”

“Just one cell?” Seymour quipped. “I’m sure they’ll feel right at home.”

“That bad, Graham?”

Seymour nodded his gray head. “At last count we were monitoring more than two hundred networks and separate groupings of known terrorists. Half our Muslim youth profess admiration for Osama bin Laden, and we estimate that more than one hundred thousand supported the attacks on the London transport system, which means they have a very large pool of potential recruits from which to draw in the future. So you’ll excuse me if I don’t sound the alarm just because another cell of Muslim fanatics has decided to put ashore.”

“Maybe it isn’t just another cell, Graham. Maybe they’re the real thing.”

“They’re all the real thing,” Seymour said. “You said you think they’re here. Does that mean you’re not sure?”