“And yet he was finally immortalized,” said Rosenblatt. “Not because of his power, but because of a poem.”

Beauvoir looked about to say something smart-ass, but stopped. And thought.

“Who was Gerald Bull?” he finally asked.

Professor Rosenblatt had unbuckled the briefcase and, after sorting through the contents, brought out some papers.

“I found these in my files after we spoke. I thought they might be needed.”

He put the papers, held together by a staple, on the coffee table.

“This is Dr. Bull.”

Isabelle Lacoste picked them up. What the professor had brought was yellowed and typewritten. There was also a grainy black-and-white photograph of a man in a suit and narrow tie, looking put upon.

“He was an armaments engineer,” said Rosenblatt. “Depending on who you speak to, Dr. Bull was either a visionary or an amoral arms dealer. Either way, he was a brilliant designer.”

“He made that thing in the woods?” asked Lacoste.

“I think so, yes. I think it was part of what he called Project Babylon. His goal was to design and build a gun so powerful it could launch a missile into low Earth orbit, like a satellite. From there it would travel thousands of miles to its target.”

“But don’t those exist?” asked Beauvoir. “ICBMs?”

“Yes, but the Supergun is different,” said Rosenblatt.

“The Meccano set,” said Lacoste. “No electronics.”

“Exactly.” The professor beamed at her. “No computer guidance systems. Nothing that depends on software or even electricity. Just good old-fashioned armaments, not that far off the artillery used in the First World War.”

“But why was that such an achievement?” asked Gamache. “It sounds like a step back, not forward. As Inspector Beauvoir says, if there’re ICBMs that can send nuclear warheads thousands of miles accurately, why would anyone want or need Gerald Bull’s Supergun?”

“Think about it,” said Rosenblatt.

They did, but nothing came to mind.

“You’re too mired in the present, in thinking that newer must be better,” he said. “But part of Gerald Bull’s genius was recognizing that ancient design could not only work, but in some cases, work better.”

“Did he also build a giant slingshot?” asked Beauvoir. “Should we be looking for one of those?”

“Think,” said Rosenblatt.

Gamache thought, and then he looked around their home. At the useless smartphone on the desk in the study. At the dial-up connection that barely worked.

He looked at the crackling fireplace, feeling its heat, and he thought about the woodstove in the kitchen. In Clara’s kitchen. In Myrna’s bookstore.

If the power went out they’d still have warmth and light. They could still cook. No thanks to modern technology. That would be rendered useless, but they’d have power because of old, even ancient, tools. Woodstoves. Wells.

Three Pines might be primitive in many ways, but unlike the outside world, it could survive a very long time without power. And that itself was powerful.