She led them back outside, where she pointed to the trees in front of the Hay-Adams Hotel. “If they were on the rooftop garden back there then the trees would’ve hidden the park from their view. They hear the sirens and the motorcade coming. They wait for it to pull in, the prime minister to get out and walk to the park. Then they start shooting.”
Stone did not look convinced. “So you’re saying this elaborate plan was put together and the gunners were firing blind?” He shook his head. “If I were going to do this, at the very least I’d have one spotter with a clear view of the PM’s movements stationed somewhere near the park with a secure line of communication. I’m not shooting blindly through tree canopies. And if the PM doesn’t come to the park, I call off the mission. But if he does set foot in the park I can’t afford to miss.”
“And they did miss everyone,” Gross pointed out.
The ATF agent nodded. “It’s a puzzler all right.”
Stone turned to him. “So if you were going to pull off this bombing, how would you detonate, Steve?”
“Pressure switches can be problematic, particularly under these conditions. I mean, you’ve got a tree in a hole and a bomb somewhere near it. Maybe in the root ball, maybe under the tree. That’s a lot of weight. And people moving stuff around, digging. Chances are that pressure switch gets tripped accidentally. And once you cover the bomb up with dirt, what’s going to trigger it? Something has to cause the switch to engage. It’s called a pressure switch for a good reason. No, if I were going to do it I’d use a command control device, meaning remote detonation. Now, if they did that they might have used a cell phone, which would make our job a lot easier. Cell phones have a SIM card and all the components are serialized, so we can reconstruct the phone and maybe track down where and who purchased it. Of course if a cell phone was used, you actually have two phones. One planted on the bomb as the switch and the other to call that phone. We did find some bits of wire, corner of a transistor, plastic shell casing, leather—”
“Leather?” Stone exclaimed.
“Yeah, tiny patches of it. About a dozen pieces. Had some black markings on them, so the probability lies with it being part of the explosive. Still trying to determine what it is. But we will. And then we have to definitively determine if it was tied to the explosion. Not all the junk we find out here will be.”
“Could have come off the jogger’s trainers,” suggested Chapman. “His shoes were made of leather, right?”
“Yes, but the color’s off. I saw the video feed and the guy’s shoes were blue.”
“The black marks could be scorching from the bomb,” Chapman pointed out.
“No, the rest of the leather was brown. Probably has nothing to do with anything.”
“So right now,” Gross said, “you still can’t tell us how the detonation was done?”
“That’s right.”
“Why are you thinking the bomb was in the tree hole in the first place?” Gross said. “Apart from the location of the damage?”
Garchik said, “Follow me.” He led them to the site of the detonation and pointed into the hole. “Unless I’m reading this wrong, this is ground zero. Blew that tree right out of here, and it wasn’t light.”
They all stared down at the hole, which had become even wider and deeper because of the explosion.
“Okay, so what are we looking for?” asked Gross.
“Well, there was already a crater here. The excavation for the tree.”
“Okay,” said Gross. “So?”
Garchik made a fist and swung it downward. “When you smack the water with your fist, a certain amount of water shoots up on both sides of the hand. Simple concept of volume displacement. Same thing happens with a bomb. If the bomb is aboveground it acts like the fist. It’ll push downward, sideways and also up. But a bomb buried in the ground has a different effect. It will propel mostly upward because it’s covered by looser dirt. Path of least resistance. It still deepened the existing hole.”
“Causing a crater. A bigger crater than if the bomb had been aboveground,” said Stone slowly.
“But the bomb in this case was buried in the dirt, right?” said Gross. He looked at each of them as though waiting for their collective affirmation.
“I wish I could tell you for certain,” said Garchik. “Normally, making that determination is one of the easiest parts of the equation. But here we have a complicating factor. There was already a big crater here before the bomb went off.”
Gross looked confused. “I’m not exactly following you here.”
Stone said, “He means he can’t tell if the bomb was buried in the dirt or may have been in the root ball or even under the tree.” He looked at the ATF agent. “Right?”
“That’s right.”
“Does it matter?” asked Chapman. “In any case the bomb was placed in the park in that hole.”
Gross said, “That’s true. The question is, how did they do it? This is Lafayette Park, not some back alley in Baghdad.”
Stone looked around. Guns and bombs right across from the president’s house. There could only be one answer. “We’ve got a traitor somewhere,” he said.
Chapman added, “And if the PM hadn’t turned his ankle he’d be dead.”
Stone looked at her. “But more to the point, they got a bomb into Lafayette Park. Across from the White House. The most heavily guarded piece of land in the world. How?”
Gross glanced at Chapman and said, “Pretty clear. British PM.”
“He wasn’t in the park,” replied Stone.
“But he was scheduled to be. At just about the time the bomb went off. It was probably on a timer, despite what Garchik said. It got accidentally triggered, probably when that guy jumped in the hole.”
Stone shook his head. “A mission like this requires precision. By detonating, even accidentally, they give away their whole plan. They won’t get a second shot. They put everyone on alert for no reason at all. And your theory doesn’t explain the gunfire.”
“It doesn’t make much sense when you explain it like that,” admitted Gross.