“Sounds like our man,” said Gabriel. “I’m betting on Edgware and influenza.”

“We’ll know in a minute.” Keller was leafing through that morning’s edition of the Times. It was filled with news of Saladin’s death.

“Can’t you at least—”

“What?”

“Never mind.”

The man from Tower Hamlets had reached the Westminster side of the bridge. He passed a Caffè Nero coffeehouse and the entrance to the Westminster Tube stop. Then he passed an undercover CBRN team and two tactical firearms officers in plain clothes. No trace of radioactivity, no detonator in the hand, no sign of emotional distress. Wrong man. He crossed the street to Parliament Square and joined a small, sad protest having something to do with the war in Afghanistan. Was it still going on? Even Gabriel found it hard to imagine.

He turned his head a few degrees to the right to watch the second man—the man from the Edgware Road section of North London—walking along Broad Sanctuary, past the North Tower of the Abbey. Keller was pretending to read the sporting news.

“How does he look?”

“Sick as a dog.”

“Something he ate?”

“Or something he’s wearing. He looks like he would glow in the dark.”

A CBRN team was on the north lawn of the Abbey, posing for photos like ordinary tourists, along with another SCO19 unit. The CBRN team had already begun to detect elevated levels of radiation, but as the man from Edgware approached, the levels spiked dramatically.

“Fucking Chernobyl,” said Keller. “We’ve got him.”

A commotion erupted over the radio, several voices shouting at once. Gabriel forced himself to look away.

“What are the odds?” he asked calmly.

“Of what?”

“That he chooses us?”

“I’d say they’re getting better by the minute.”

The man crossed Broad Sanctuary to the Supreme Court building and entered Parliament Square at the southwest corner. A few seconds later, sweating, lips moving, pale as death, he was approaching the bench on which Gabriel and Keller sat.

“Someone needs to put that poor bloke out of his misery,” said Keller.

“Not without an order from the prime minister.”

The man walked past the bench.

“What level of exposure did we just suffer?” asked Keller.

“Ten thousand X-rays.”

“How many have you had?”

“Eleven thousand,” said Gabriel. Then he said quietly, “Look at the left hand.”

Keller did. It was clutching a detonator.

“Look at his thumb,” said Gabriel. “He’s already putting pressure on the trigger. Do you know what that means?”

“Yeah,” said Keller. “It means he’s got a dirty bomb with a dead man’s switch.”

Big Ben was tolling nine o’clock when the martyr-in-waiting reached the eastern flank of the square. He paused for a moment to watch the protest and, it seemed to Gabriel, to consider his options—the Palace of Westminster, which was directly before him, or Whitehall, which was to his left. The prime minister and his security aides were considering their options as well. At this point, there was only one. Someone had to grant the man the death he so badly wanted while someone else held his thumb tightly to the detonator switch. Otherwise, several people would die, and the seat of British power and history would be a radioactive wasteland for the foreseeable future.

At last, the martyr-in-waiting turned to the left toward Whitehall, with Gabriel and Keller trailing a few steps behind. A gentle breeze blew from the north directly into their faces—a breeze that would disperse the radioactivity all over Westminster and Victoria if the bomb detonated. The CBRN team that had been at Caffè Nero was now standing outside the Revenue and Customs building; their readings were off the charts as the man walked past them. It was all the proof the prime minister needed. “Take him down,” he said, and the head of the Counter Terrorism Command repeated the order to Gabriel and Keller. Then he added quietly, “And may God be with you both.”

But on whose side, thought Gabriel, was God on that morning? On the side of the fanatic with a weapon of mass destruction strapped to his body, or the two men who would try to prevent him from detonating it? The first move was Keller’s to make. He had to seize the left hand of the martyr in an iron-lock grip before Gabriel fired the kill shot. Otherwise, the martyr’s thumb would weaken on the detonator switch and the bomb would explode.

They passed the archway of King Charles Street and the entrance of the Foreign and Commonwealth Office. The traffic along Whitehall dwindled. Evidently, the police had blocked it off at Parliament Square to the south and Trafalgar Square to the north. The martyr-in-waiting seemed not to notice. He was walking toward destiny, walking toward death. Gabriel drew the Glock pistol from the small of his back and quickened his pace while Keller, a blur in his peripheral vision, drew a few deep breaths.

Before them, the sweating, radiation-sickened martyr passed unseeing through a knot of tourists and started toward the security gate of Downing Street, his apparent target. He slowed to a stop, however, when he saw the black-uniformed police officers standing on the pavement. At once, he noticed the peculiar absence of cars in the normally busy street. Then, turning, he saw the two men walking toward him, one with a gun in his hand. The eyes widened, the arms rose and stretched shoulder-width from each side.