“Oh, no. They were right. Baby Babylon didn’t work. It was top-heavy, couldn’t sustain trajectory. With something like that, firing a missile into low orbit and having it travel tens of thousands of miles, if you’re off by one one-thousandth of a degree at launch, you wipe out Paris instead of Moscow on impact. Or Baghdad.”

“Or Bethlehem.”

Rosenblatt didn’t respond to that.

“How did they know it didn’t work?” asked Gamache.

“They fired it.”

Gamache didn’t, or couldn’t, hide his surprise.

“Not into the air,” Rosenblatt hurriedly assured him.

“Then where?” asked Gamache.

“Into the ground.”

Now Gamache looked, and was, confused.

“When you were there, did you happen to notice railway tracks?” the professor asked. “Not the Canadian National ones, but smaller, narrower?”

“Yes. I followed them up the hill.”

“Good. That’s how Bull did it. As with everything else about Project Babylon, it was brilliant in its simplicity. They couldn’t possibly test the missile launcher by actually launching a missile, so they put it on a flatbed on rails at the bottom of a hill and fired it into the ground.”

“What good would that do?” asked Gamache.

“The backward force,” said Rosenblatt. “They measured the degree of incline, the speed and distance traveled, and the depth and trajectory of the hole in the ground. It was so simple it was genius.”

“It doesn’t sound simple to me,” Gamache admitted. Rosenblatt had lost him at “degree of incline.” Gamache considered what he’d heard.

“Wouldn’t it make a lot of noise?” he asked. “So much for secrecy.”

“Yes,” agreed Rosenblatt. Gamache waited for more, but nothing more came.

“It didn’t work, you say?”

“They tried it a few times, apparently, but while the force could be corrected, they couldn’t solve the trajectory problem. Eventually they abandoned the site.”

That sounded like the end of the story, but Gamache knew it was really just the beginning. They weren’t even at the end now, thirty years later. But he had a feeling they were approaching it. Or it was approaching them.

“What happened next?” he asked.

“Project Babylon was closed down. Gerald Bull moved to Brussels and Guillaume Couture retired to his roses.”

“Except that Project Babylon wasn’t over,” said Gamache. “In fact, it got bigger. You say not many knew about the next phase?”

“That was the only thing that was disconcerting. Gerald Bull was guarded about the second weapon, Big Babylon. It was unlike him. He was a snake-oil salesman, a huckster. So when he was quiet about this second design, it got some people wondering.”

“If it was true,” said Gamache.

“If Gerald Bull was building an even more dangerous weapon, and playing an even more dangerous game. With even more dangerous people.”

“More dangerous than the Iraqis?”

Michael Rosenblatt didn’t answer that.

Gamache thought for a minute. “If Bull didn’t talk about it, how did people find out?”