"A tragedy all around," the president said numbly, still looking down at Tippi.

"We should do this," Jane said. "And then get out of here. And get Willa back."

"Honey, if Waters is right about what he told us in the chopper, then we won't be getting Willa back."

"What do you mean?"

"He wants to kill us. This Quarry fellow. He may try to do so when we leave here."

"How can he? We're surrounded by an army. We're always surrounded by an army."

"I don't know, but if that was his intent all along? He'll certainly try."

"So what are you saying?"

"That we need to focus on us surviving this. If there is an assassination attempt and it fails he'll know about it. He'll kill Willa, if she's not already dead. But then he'll also try to reveal what happened. We have to be prepared for that. We have to concoct an alternative. Whatever proofs he might think he has, I know my people can counter them. He's just one man. I have an army of spin masters."

"He may be only one man, but look what he's done so far."

"That doesn't matter. It only matters how it ends. Now let's do what Quarry asked us to do and get out of here."

They stood in front of the bed and held hands.

Jane spoke first. "I'm sorry, Tippi. I never intended for this to happen. I'm truly sorry."

The president cleared his throat. "I hope you will forgive me for what I did to you. I… it's not enough to say that I don't remember, or that I wasn't myself. It was my responsibility. And I'll have to live with that for the rest of my life. I'm sorry too, Tippi. Deeply, deeply sorry."

Jane lightly touched Tippi's hand. The president started to do the same thing, but then apparently thought better of it and withdrew his fingers.

They turned to the doorway.

The HRT squad was a few feet away, Foster, Waters, and the Secret Service team right behind them, all poised to act on a second's notice. In the bunker Carlos clearly saw the couple on the monitor.

He punched the single button on the remote. This caused two things to happen simultaneously.

The left side of the doorjamb was blown out as a nearly two-inch-thick metal door hidden in the cavity of the wall there sprang forth, powered by a hydraulic propulsion system concealed in the wall behind the lead sheathing. This action sealed the First Couple in the room.

Then, inside the room, there was a hissing sound. Around the perimeter of the interior were holes carefully precut into a metal lining underneath the subfloor. This was what the HRT drill had hit, not the cement, but a second subfloor hidden away in a cavity of the foundation. Inside this cavity were a series of connected metal cylinders containing nitrogen gas. They had been hooked to the splitter cable Quarry had run up through the PVC pipe in the foundation, and then triggered by the remote. The gas rose up through the holes in the metal and then passed through the narrow gaps in the floorboards. The tanks were under great pressure and deployed their contents with force. Soon the small space was filled with nitrogen gas.

Nitrogen occurs naturally, but it also depletes oxygen and in certain circumstances can be lethal. Humans exposed to unsafe levels of the gas don't feel any pain. They lapse into unconsciousness quickly and without really realizing what is happening. They are never aware that in a very few minutes they will suffocate as the oxygen is displaced. For this reason countries that were rethinking bringing back the death penalty were looking at deploying nitrogen in a gas chamber because it worked so quickly and painlessly.

They would do well to have studied Sam Quarry's model, since the man from Alabama had built the perfect execution chamber disguised as a shack.

Tippi's life support system included an oxygen converter and oxygen tank that together fed a mixture of pure and room-mixed oxygen into the ventilator trach tube and from there into her lungs. The mixture was very carefully calibrated, only now there was no oxygen left in the room. And the amount of pure oxygen coming from the tank wasn't nearly enough to make up the difference. In her terribly weakened condition, she expired almost immediately. The monitor screeched this result as she flatlined. Her hell on earth was finally over.

Outside, the frantic HRT squad and the Secret Service team were deploying every tool they had to get the door open short of opening fire or detonating a bomb, either of which could kill the people inside. They attacked the metal door and the walls, only to find welded metal under the boards. Men in suits next to men in fatigues clambered onto the roof with axes and chain saws but their efforts were blunted by heavy shingles and sheets of metal screwed down into thick wood. The little house was nearly impenetrable.

Yet they never gave up on their assault. Eight minutes later, using power saws, sledgehammers, a hydraulic battering ram, and pure sweat and muscle, they managed to knock down the metal door. Five men rushed in and then immediately rushed back out gagging from the lack of oxygen. Other agents donned oxygen masks and ran inside.

When they came out a few seconds later, Carlos, watching on the monitor, cursed. The president and the First Lady were pulling off their oxygen masks with attached small cylinder tanks that Jane had carried under her coat. They had been given to them by Agent Waters acting on the tip from King after he'd discovered the extra nitrogen gas cylinders in Quarry's basement and deduced what they might be used for.

Foster and his men ran to the First Couple and escorted them so rapidly back to the chopper that neither the man nor the woman's feet seemed to touch the ground.

"Are you all right, Mr. President?" asked Foster anxiously after they were safely inside the chopper. "We'll need to get you and the First Lady checked out medically."

"I'm fine. We're fine." He eyed Chuck Waters. "Good call. We put the masks on as soon as the gas started coming in."

"That was Sean King's doing, sir, not mine. But even then, I didn't think the gas would be in that house. We thought it was all clear."

"Well, I'll have to thank Mr. King." He glanced at his wife. "Again."

A pale Foster added, "If I suspected for a second that the place was booby-trapped like that, sir, I never would have let you go in."

Cox slipped the gun from his waistband and handed it back to Foster. "Well, I really didn't give you a choice, did I? Whoever put that thing together was extremely clever. From the sophistication of the plot, it seems that a well-funded terrorist organization was behind this. And my stupid antics really put you between a rock and a hard place, Larry. I'm sorry."

Foster's face reddened. It was rare for a president to apologize to anyone, much less a Secret Service agent.

"Apology accepted, Mr. President." The two men shook hands.

As the door to the chopper slammed shut, the president said, "We need to get back to D.C. pronto."

"I couldn't agree more, Mr. President," said a relieved Foster.

"And your niece?" said Waters.

"After what just happened, there seems little hope of her still being alive. If their goal was to kill me, they obviously never intended to release her."

Jane Cox let out a sob and covered her face. The president put a supportive arm around her. "But we must continue to do everything we can." He looked around the interior of the chopper. "We must not give up hope. But we must also prepare for the worst. Those bastards tried to kill me and my wife today, but they failed. America will never give in to evil like this. Never. They can keep trying to get to me, but I will never let them win. Not on my watch."

Every agent on the chopper looked at Dan Cox with immense pride, forgetting that a few minutes ago he'd been a raging madman with a gun pressed to his temple, more worried about being reelected than getting his niece back. He had bravely walked into what turned out to be a trap in order to save his niece. And now, having barely escaped death, he was being supportive of his wife and rallying the troops. That was some serious street cred that U.S. presidents typically never earned.