But there is a difference between fear-which, reined in and redirected, can fuel intense concentration-and anxiety. Anxiety, in the form of uncontrollable apprehension and distress, is the most dangerous thing a member of a bomb squad can face, far more perilous than any bomb. A bomb is logical (whether or not we understand its logic), and a person with anxiety is not.

Dr. Payne and Lieutenant Colonel Suarez and the twenty-eight other NEST members who lined the stairwell were professionals and were experienced in rendering bombs safe. Still, each one was deeply frightened. There was far too much about this bomb that was unknown.

Simply put, they did not know whether the bomb was set to detonate if anyone came near it. The fusing mechanism had been intensively examined in a Department of Energy laboratory to determine how much energy it would take to set off the detector, whether there was a sensitivity switch or a variable resistor. Dr. Payne had himself plotted the RF (radio frequency) emanation relative to the position of gain control. He knew how much motion would set the thing off. He knew that it was designed not to respond to motion beyond twenty-five feet.

But he didn’t know whether the sensor had been dialed up, extending the safe line to forty or fifty feet or more. And it was possible the sensor wasn’t even on.

He had no idea.

This much he knew for sure: his men had not set off the bomb. Wherever the safe line was, they hadn’t stepped over it.

But it might be located at the doorjamb, and they would have to assume that it was.

If there was indeed a proximity detector in force, Payne thought, most likely it affected the area on the other side of the door. Microwaves, for all practical purposes, do not go through steel.

But to be safe, they could not risk encroaching even an inch beyond where the closest man-Dr. Payne-was standing. All of their tests had to be conducted from their present positions, and no closer.

The first order of business for the team was to rule out the presence of a nuclear weapon. To do that, they had to test for radioactivity. Not knowing what was in the nuke, or even if it was a nuke at all, they had no way of knowing whether to test for alpha or beta particles, or gamma waves, or for neutron emission. Each is detected by means of a separate procedure. They could test either for whatever radioactive substance was in the bomb or for the “degradation material,” the substance the bomb material would degrade into.

Dr. Payne knew they were not close enough to test for alpha or beta emissions. That left neutrons and gamma. If their detectors “smelled” a large quantity of gamma waves and a small quantity of neutrons, they were probably dealing with uranium; if they “smelled” the opposite, it was probably plutonium.

Their tests told them that the bomb inside the steel door was not nuclear.

That was a relief, though it lasted only a few seconds.

***

In a darkened room on the building’s fifth floor, Baumann was working with a soldering iron and a pair of wire cutters. Jared, his arms and legs bound, wriggled on the floor a few feet away, thumping his duct-taped feet against the floor in an ineffectual attempt to summon someone, anyone. But the floor was tile over concrete, and the thumping made barely a sound, and in any case, the top floors of the building were by now evacuated. There was no one on the floor to hear him.

Baumann continued to work, his concentration undisturbed.

CHAPTER NINETY-FOUR

The next order of business for the NEST men was to determine whether the microwave detector had indeed been turned on. If not, they could force open the steel door and safely approach the bomb to render it safe.

If it was…

Well, the first thing was to determine whether it was on or not. To do that, they used a device known as a microwave sniffer, which looks for emanations in the microwave wavelength, above ten gigahertz. A version of this same device is used to test kitchen microwave ovens for leaks.

A junior member of the team, an Army sergeant named Grant who was trained in explosives detection, took the microwave sniffer’s long, flexible antenna and pointed it at the steel door as Payne directed him to do.

“Dr. Payne,” he said, “we’re just not going to get anything. This door here is steel, and microwaves are pretty much blocked by steel, sir. It’s going to mask the microwave emanations.”

“That’s right,” Payne said. “But keep at it, please.”

Sergeant Grant had served in the Army long enough to know how to take orders with grace, so he continued, though with a trace of reluctance. The microwave sniffer was silent.

“You want me to sort of snake this antenna under the door?”

“No, Grant. That’s a huge risk. Bad idea.”

“Sir,” Grant said, “Like I said, this here door-” But he was interrupted by a rapid, high-pitched beeping. The sniffer had gone into alarm mode.