“But the main thing is,” said Lacoste. “It isn’t armed, and even if it was, it can’t be fired.”

“Not without the mechanism, no.”

“What would it look like?” Gamache asked.

“The trigger would have cogs that fit onto this wheel.” The professor pointed to a circle with teeth, about a foot wide. “There’s nothing electronic on this thing. Not even the guidance system. It’s all done manually.”

“Could it have fallen off?” asked Beauvoir, looking on the ground.

“This isn’t a LEGO set. Things don’t just fall off. It’s intricate, perfectly made. Each piece fits snugly, exactly.”

“So, no?” said Beauvoir.

“No,” said Rosenblatt. “If it’s gone, someone took it, and by the looks of it, not recently. I need to see the etching again.”

The elderly man spoke with determination and Gamache realized that while he was afraid of heights, and Beauvoir was afraid of confined spaces, Professor Michael Rosenblatt was afraid of the etching.

They walked back to it, and Rosenblatt stepped back, taking in the winged monster as it reared and bucked. Its seven heads were straining, its long necks intertwining like serpents. There was a woman on its back, holding reins. Controlling the beast. She stared out at them, a strange expression on her face. It wasn’t wrath, thought Gamache. It wasn’t vengeance or blood lust. It was more sinister. Something Gamache couldn’t quite define.

Professor Rosenblatt whispered under his breath.

“What did you say?” asked Gamache, who was closest to the scientist.

Rosenblatt pointed to what looked like scales on the monster’s body.

Gamache stepped closer, then, putting on his glasses, he bent in. Straightening up, he looked at the professor.

“Hebrew?”

“Yes. Can you read it?” asked Rosenblatt.

“No, I’m afraid not.”

Rosenblatt looked again at the creature. At the detailing, which were not scales at all, but words. And he read, out loud.

Then he turned to his companions in this dark place. He looked both triumphant and terrified. As though his worst fear and greatest wish were one and the same. And had come true.

“By the waters of Babylon,” he said, “we sat down and wept.”

The blood rushed from Gamache’s face. In front of him the gun glowed, unnaturally, supernaturally, in the floodlights. Shadows were thrown on the canopy, a false sky above, a grotesque constellation.

“Now,” said Professor Rosenblatt, “I can tell you what this is.”

*   *   *

They sat in the living room of the Gamache home, around the fireplace where flames leapt and danced and threw cheerful light on the somber faces.

It had been cold in the forest, and the decision was made to return to someplace warm. And private.

They sat with mugs of tea, warm and comforting, and plates of madeleines Armand had picked up at Sarah’s boulangerie as they’d passed by.

“What you’ve found,” said Professor Rosenblatt, “is Project Babylon. When we spoke this morning and you described it, I barely believed you. Project Babylon is a tale physicists told to scare each other. It’s a Grimms’ tale for scientists.”

He took a deep breath and tried to cover his discomfort by reaching for another pastry. But his unsteady hand betrayed him.

Gamache couldn’t decide if the tremble was caused by fear or excitement.

“What you have is a Supergun. No, not ‘a’ Supergun, it’s ‘the’ Supergun. The only one of its kind. Within the armaments community it’s a sort of legend. For years we’d heard rumors that it’d been built. Some people tried to find it, but gave up. Then the talk died away, as time passed.”

“When you first saw it,” said Gamache, “you whispered, ‘He didn’t.’ Who did you mean?”

Armand leaned forward, forearms on his knees, his large hands forming a sort of bow in front of him. Like a ship plowing through the seas.

“I meant Gerald Bull,” said Rosenblatt, and seemed to expect some sort of reaction. A gasp, perhaps. But there was nothing beyond rapt attention.

“Gerald Bull?” Rosenblatt repeated, looking from one to the other to the other.

They shook their heads.

“Look on my works, ye Mighty,” said Rosenblatt as he drew his battered leather briefcase toward him. “And despair.”

“Oh no,” sighed Beauvoir. “Now we have two of them.”

“‘Ozymandias,’” said Gamache, looking at Jean-Guy with despair. “The professor was quoting a sonnet by Shelley—”