“The weapon needs no power source,” said Gamache slowly. Coming to the realization, and the implication. “It can send a missile into orbit without even a battery.”

Professor Rosenblatt was nodding. “That’s it. The brilliance and the nightmare.”

“Why nightmare?” asked Beauvoir.

“Because Dr. Bull’s Supergun meant any terrorist cell, any extremist, any crazy dictator could become an international threat,” said the scientist. “They didn’t need technology, or scientists, or even electricity. All they’d need was the Supergun.”

He let that sink in, and as it did even the cheery fireplace couldn’t take the chill out of the room, or wipe the alarm from their faces.

“But maybe he didn’t do it,” said Lacoste. “Maybe he wasn’t successful. Maybe Bull abandoned it because it doesn’t work.”

“No,” said Professor Rosenblatt. “He abandoned it because he was killed.”

They stared at him.

“How?” asked Gamache.

“He was murdered in 1990. Some describe it as an assassination. He was living in Brussels at the time. Five bullets to the head.”

“Professional,” said Lacoste.

Rosenblatt nodded. “The killers were never caught.”

Gamache’s eyes narrowed in concentration.

“I seem to remember this,” he said. “Gerald Bull was a Quebecker—”

“Actually, he was born in Ontario and studied at Queens University. It’s all in there.” Rosenblatt waved at the papers he’d brought them. “But he did much of his work here in Quebec. At least, at first.”

“Did you know him?” asked Gamache.

“Not really. He was at McGill for a short while. Considered a bit of a crank. Difficult.”

“Unlike physicists?” asked Gamache, and saw Rosenblatt smile.

“I’m afraid I’m not brilliant enough to be difficult,” he said. “That’s reserved for geniuses. I was just an academic, teaching students about trajectory. Or trying to. When sophisticated systems came in, students realized they didn’t really have to know these things. Computer programs would do it all for them. I might as well have been using a slide rule and an abacus.”

“Dr. Bull never came to you for advice?” Gamache prodded.

Now Rosenblatt laughed outright. “Advice? Gerald Bull? No. And he wouldn’t have come to me anyway. I was much too lowly.”

The two men regarded each other before Gamache finally smiled and dropped his eyes. But Michael Rosenblatt took warning, and wondered if he might have just overdone it.

“The chatter after he’d died was that Bull had in fact built the Supergun,” said Rosenblatt. “And it was ready to be tested. But no one knew where it was. And it was all just gossip. People like drama but no one really believes it.”

“Why was he killed?” Beauvoir asked.

“No one knows for sure, of course,” said Rosenblatt. “The assumption was he was killed to stop him from building the gun.”