“If the Supergun is really just a huge cannon,” said Gamache, “would it fire only conventional missiles or could it be adapted?”

“It would fire anything put into it.”

Gamache paused to absorb that statement, said so matter-of-factly.

“Including a nuclear warhead?”

Rosenblatt shifted a little in his seat and nodded.

“Chemical weapons?” asked Gamache.

Another nod.

“Biological weapons?”

Now Rosenblatt leaned forward. “It would shoot a Volkswagen into the lower atmosphere. It would carry whatever the person firing it wanted.”

That was followed by silence.

“So what’s it doing here?” Gamache asked.

More silence, until Rosenblatt finally spoke, quietly. “I don’t know.”

“Guess.”

“I won’t guess. I’m a scientist. Guessing isn’t part of what I do.”

Gamache smiled. “Of course it is. Scientists come up with theories all the time. What are they except best guesses? Try. It’s not as though you haven’t been sitting here wondering the same thing.”

Professor Rosenblatt took a deep breath. “It could be a prototype, something to show buyers. That might explain why the firing mechanism is missing. It’s not meant to be fired. It’s meant as a sort of mock-up. A sales tool.”

“Or?”

“Or it’s meant to be fired. Did you notice where it’s pointed?”

“Into the United States,” said Gamache. “Which theory do you think is most likely? A mock-up, or built to be used?”

Rosenblatt shook his head. “The missing firing mechanism is a puzzle. Was it never made? Was it removed?” He looked into Gamache’s face. “I honestly don’t know.”

Armand Gamache wasn’t sure he believed the scientist, but he knew he would not, at this point, get a clearer answer.

“The good news is we found the Supergun before it could be fired, if that was the intention,” said Gamache. “Unfortunately, it cost Laurent Lepage his life.”

Professor Rosenblatt looked closely at his companion. “You’re retired. What’s your interest in this?”

“Laurent was my friend.”

Rosenblatt nodded. The statement was simple. Elegant. And as powerful as the gun.

“And now you’re out for revenge?” asked Rosenblatt.

Gamache tilted his head slightly. “I hope that’s not it.”

Now it was Rosenblatt’s turn to tilt his head. “But you’re not sure.”

“Anything interesting in the papers you borrowed?” Gamache asked, his voice clipped.

Rosenblatt looked at him for a moment, then dropped his gaze to the pages.

“A shame about the blacked-out bits, but I don’t think there’s really anything in here that isn’t common knowledge.”

“Common?”

“Since Bull’s death and with the passage of time, some information has come out about his work,” said Rosenblatt. “I’m sure you’ve found some yourselves now that you know the key words. But there’re still some things only people in the field know, or guessed.” Rosenblatt paused a moment. “Theorized.”

“And what field would that be?”