It took two minutes for Gabriel to dress and get the Beretta and another minute to make his way downstairs to the street. The traffic signal along the Bayswater Road was blinking red when he arrived. He ignored it and sprinted through the oncoming traffic into the park. Just then he heard the rumble of an explosion deep underground and felt the earth shift suddenly beneath his feet. He stopped for a moment, uncertain of what he had just heard and felt, then turned and raced toward the center of the park.

Chris Petty slowed to a stop and pulled the phone out of the clip attached to the waist of his sweatpants.

“You guys go ahead,” he called out. “Take the usual route. I’ll catch up if I can.”

The rest of the group turned away from the shore of the Serpentine and headed into the stand of trees north of the lake. Petty looked at the caller ID screen. It was his office inside the embassy. He opened the phone and brought it quickly to his ear.

“Petty.”

Static …

“This is Chris Petty. Can you hear me?”

Silence …

“Shit.”

He killed the connection and set off after the others. Twenty seconds later the phone rang again. This time, when he raised it to his ear, the connection was perfect.

The man in the Addison amp; Hodge uniform collecting rubbish along the pathway looked up as the group of runners turned onto the footpath leading from the Old Police House to the Reformers’ Tree. The second false Addison amp; Hodge van was parked on the opposite side of the path, and another uniformed man was scratching at the earth with a rake. They had been preparing for this moment for over a year. Thirty seconds , the operational planner had said. If it lasts more than thirty seconds, you’ll never make it out of the park alive . The man reached into the plastic rubbish bag he was holding in his hand and felt something metallic and cold: a Heckler amp; Koch MP7 machine pistol, loaded with forty armor-piercing rounds. He blindly thumbed the fire-selector switch to the proper setting and counted slowly to ten.

Whether it was by design or accident, Chris Petty failed to terminate the telephone call from the embassy before setting off in pursuit of his colleagues. He saw them almost immediately after making the turn at the Old Police House. They had covered about half the distance to the Reformers’ Tree and were approaching a pair of forest green Ford Transit vans parked along the edge of the path. It was not unusual to see workmen in the park early in the morning-Hyde Park was 350 acres in size and required near-constant care and maintenance-but their true purpose was revealed a few seconds later when the rear cargo doors swung open and eight well-armed men in black jumpsuits and balaclava hoods poured out. Petty’s futile warning shouts were heard and recorded inside the RSO ops center, as was the sound of gunfire and screaming that followed. Petty was hit ten seconds after the initial burst and his death agonies were captured on the center’s digital recorders. He managed to say only one word before succumbing to his wounds, though it would be several minutes before his stricken colleagues inside the embassy understood its meaning. Gardeners …

Gabriel heard the first shots while he was still in the open ground at the northern edge of the park. He drew his Beretta as he sprinted into the trees, then stopped on the footpath and looked in the direction of the Reformers’ Tree. Fifty yards away was a scene from his nightmares: bodies on the ground, men in black jumpsuits pulling a struggling woman toward the back of a waiting van. He raised the gun but stopped himself. Was this truly the attack or had he stumbled into a police drill or the set of an action film? Were the men in black really terrorists or were they police officers or actors? The closest body lay thirty yards away. On the ground next to the man were a mobile phone and a SIG-Sauer P226 9mm pistol. Gabriel crept quickly to the fallen man’s side and knelt beside him. The blood and bullet wounds were real, as was the look of death in the man’s frozen eyes. He knew then that this was not a drill or a film set. It was the attack he had feared, and it was unfolding before his eyes.

The terrorists had not noticed him. Gabriel, still on one knee, leveled the Beretta in both hands and took aim at one of the black-suited men pulling the woman toward the van. It was thirty yards, a shot he had made countless times before. He squeezed his trigger twice in quick succession, tap-tap , just as he had been trained to do. An instant later there was a flash of pink and the man spiraled lifelessly to the ground, like a toy released by the hand of a child. Gabriel moved his aim a degree to the right and fired again. Another flash of blood and brain tissue. Another attacker gone.

This time there was answering fire. Gabriel rolled off the footpath and took cover behind the trunk of a tree as a hailstorm of gunfire tore the bark to shreds. When the firing stopped, he pivoted from behind the tree and saw that the terrorists had succeeded in getting the woman into the back of the van. One was closing the rear cargo door; the others were scurrying toward the second van. Gabriel took aim at the one closing the door and fired. The first shot hit the terrorist in the left shoulder blade, spinning him around. The second struck in the center of the chest.

The vans shot forward and started across the broad green, toward Marble Arch and the busy intersection at the northeast corner of the park. Gabriel rose to his feet and sprinted after them, then stopped and fired several shots into the back of the van that he knew contained only terrorists. The vans continued toward the perimeter of the park. Gabriel gave chase for a few more seconds; then, realizing he could not possibly close the gap, he turned and ran back to the site of the assault.

Nine bodies lay scattered over the blood-soaked footpath. The six Americans were all dead, as were the two terrorists that Gabriel had taken down with head shots. The one who a moment ago had been forcing the woman into the back of the van now lay gasping for breath, blood pouring from the mouth of his balaclava. Gabriel kicked the machine pistol from his grasp and tore the hood from his head. The face staring up at him was vaguely familiar. Then he realized it was Samir al-Masri, the Egyptian from west Amsterdam.

The Egyptian’s eyes were beginning to lose focus. Gabriel wanted something from him before he died. He lifted the Egyptian by the front of his jumpsuit and slapped him hard across the face.

“Where are they taking her, Samir? Tell me what you’re going to do with the girl!”

The eyes focused for a moment.

“How do you know my name?”

“I know everything, Samir. Where are they taking the girl?”

He managed a mocking smile. “If you know everything, then why are you asking me?”

Gabriel hit him again, harder this time, and shook him so violently he feared he may have broken his neck. It didn’t matter. Samir was dying. Gabriel pointed the gun into his face and screamed, “Where are they taking her, you motherfucker! Tell me before I blow your head off!”

But Samir only smiled again, not a mocking smile but the sublime grin of a man who had achieved his desire to die. Gabriel had brought him to death’s doorway and was only too happy to see him through to the other side. He placed the barrel of the Beretta to the terrorist’s face and was about to pull the trigger when he heard a voice behind him shouting: “Drop the gun and put your hands in the air.”

Gabriel released the Egyptian, then laid the Beretta on the ground and slowly raised his hands. His memory of what transpired next would be vague at best. He remembered being driven forward into the ground and could recall the sight of Samir’s dead eyes staring into this own. Then someone hit him in the back of the head, a heavy blow that seemed to split his skull in two. He felt a burst of excruciating pain and saw a flash of brilliant light. Then he saw a woman, a woman in a dark blue tracksuit, being led into a valley of ashes by murderers in black hoods.

The telephone call arrived in the Family Quarters on the second floor of the White House at 3:14 A.M. The president snatched the receiver from the cradle after the first ring and brought it quickly to his ear. He immediately recognized the voice at the other end of the line: Cyrus Mansfield, his national security advisor.

“I’m afraid there’s been another attack in London, Mr. President.”

“How bad?”

Mansfield answered the question to the best of his ability. The president closed his eyes and whispered, “My God.”

“The British are doing everything they can to seal off London and prevent them from escaping,” Mansfield said. “But as you might expect, the situation is extremely chaotic.”

“Activate the Situation Room. I’ll be downstairs in five minutes.”

“Yes, sir.”

The president hung up the phone and sat up in bed. When he switched on the bedside lamp, his wife stirred and looked at his face. She had seen the expression before.

“How bad?” she asked.

“ London has been hit again.” He hesitated. “And Elizabeth Halton has been taken hostage.”