“Can I go back now?” asked Nichol, weary of amateurs.

Gamache stared at the screen, still feeling uneasy. But he nodded.

*   *   *

The full shift was called in and every desk and monitor in the Cyber Crimes division had an agent at it.

“But, ma’am,” Charpentier was appealing to his boss, “it was a ghost. I’ve seen thousands of them—so have you. I took a good look, just to be sure. Ran all the security scans. Nothing.”

Lambert turned from her shift commander to the Chief Superintendent.

Unlike Charpentier, Chief Inspector Lambert knew how critical the next few hours would be. The firewalls, the defenses, the software programs she herself had helped design needed to be impenetrable. And they were.

But Francoeur’s concern had transferred itself to her. And now she wondered.

“I’ll make sure myself, sir,” she said to Francoeur. He held her eyes, staring at her for so long, and so intently, that both Tessier and Charpentier exchanged glances.

Finally Francoeur nodded.

“I want your people to not just guard, do you understand? I want them to go looking.”

“For what?” Charpentier asked, exasperated.

“For intruders,” snapped Francoeur. “I want you to hunt down whoever might be out there. If there’s someone trying to get in, I want you to find them, whether they’re a raccoon or a ghost or an army of the undead. Got it?”

“Got it, sir,” said Charpentier.

*   *   *

Gamache reappeared at Nichol’s elbow.

“I made a mistake,” he said right into her ear.

“How?” She didn’t look at him but continued to concentrate on what she was doing.

“You said it yourself, the file was old. That means Aqueduct was an old company. It might not exist anymore. Can you find it in archives?”

“But if it doesn’t exist how can it matter?” asked Nichol. “Old file, old company, old news.”

“Old sins have long shadows,” said Gamache. “And this is an old sin.”

“More fucking quotes,” mumbled Nichol under her breath. “What does it even mean?”

“It means, what started small three decades ago might have grown,” said the Chief, not looking at Agent Nichol, but reading her screen. “Into something…”

He looked at Nichol’s face, so flat, so repressed.

“… big,” he finally said. But the word that had actually come to mind was “monstrous.”

“We’ve found the shadow.” Gamache turned back to the screen. “Now it’s time to find the sin.”

“I still don’t understand,” she muttered, but Gamache suspected that wasn’t true. Agent Yvette Nichol knew a great deal about old sins. And long shadows.

“This’ll take a few minutes,” she said.

Gamache joined Superintendent Brunel, who was standing by the window looking at her husband, clearly longing to watch over his shoulder.

“How’s Jérôme doing?”

“Fine, I suppose,” she said. “I think tripping that alarm shook him. It came earlier than he expected. But he recovered.”

Gamache looked at the two people seated at their desks. It was almost seven thirty in the morning. Six hours since they’d begun.

He walked over to Jérôme. “Would you like to stretch your legs?”

Dr. Brunel didn’t answer at once. He stared at the screen, his eyes following a line of code.

“Merci, Armand. In a few minutes,” Jérôme said, his voice distant, distracted.

“Got it,” said Nichol. “Les Services Aqueduct,” she read, and Gamache and Thérèse leaned over her shoulder to look. “You were right. It’s an old company. Looks like it went bankrupt.”

“What did it do?”

“Engineering mostly, I think,” she said.

“Roads?” asked Thérèse, thinking of the alarm Jérôme had tripped. The road construction schedule.

There was a pause while Nichol searched some more. “No. Looks like it’s sewage systems, mostly in outlying areas. This was in the days when there was government money to clean up the waste dumped into rivers.”

“Treatment plants,” said Gamache.

“That sort of thing,” said Nichol, concentrating on the screen. “But see here,” she pointed to a report. “Change of government. Contracts dried up, and the company went under. End of story.”