His eyes shifted across the plan, to the opposite arm. With the chocolate factory, the dining hall, the kitchens. And another walled enclosure.

“What’s this, mon père?” The Chief pointed.

“That’s our vegetable and herb garden. We grow our own, of course.”

“Enough to feed all of you?”

“That’s why we’ve never had more than two dozen monks. It was judged by the founders to be the perfect number. Enough to do the work, and not too many to feed. They were right.”

“And yet you have thirty cells. Room for more. Why?”

“Just in case,” said Dom Philippe. “As you so rightly said, Chief Inspector, we’re an order of fretters. Suppose we needed more space? Suppose someone came? We’re prepared for the unexpected. Though the perfect number is twenty-four.”

“But now you’re down to twenty-three. A spot has opened up.”

“I suppose it has. I hadn’t thought that far ahead.”

The Chief Inspector wondered if that was true, and wondered if that might make a motive. If the abbot did the recruiting, could he have found another monk he wanted to invite to join the Gilbertines?

But someone would have to go before the new person could come. And who better than the troublesome prior?

Gamache tucked that possibility away, but without any great enthusiasm. Even in the cutthroat world of universities, or New York co-ops, where there were finite places, people rarely actually cut throats. Or bashed in skulls.

He could see many reasons this abbot might kill his prior, but to open up a space for someone else seemed among the least likely.

“Who was the last person you recruited?”

“Brother Luc. He came just under a year ago, from an order close to the American border. They’re also a musical order. Benedictines. Make wonderful cheese. We trade chocolate for their cheese. You had some at breakfast.”

“Delicious,” agreed the Chief, who wanted to get off cheese and back to the murder. “Why did you choose him?”

“I’d had my eye on him since he entered the seminary. Beautiful voice. Extraordinary voice.”

“And what else does he bring?”

“Pardon?”

“I understand that singing might be what you look for first—”

“I look for piety first,” said the abbot. His voice was still pleasant, but there was no mistaking his tone. He wanted to make that clear. “First I must believe that a brother will fit in with the goal of Saint-Gilbert, to live with God through Christ. If that’s satisfied, then I look at other things.”

“Like his voice,” said Gamache. “But there has to be more, non? Another skill he brings. As you say, you need to be self-sufficient.”

For the first time, the abbot hesitated. Looked uncomfortable.

“Frère Luc has the advantage of youth. He can be taught.”

But Gamache had seen the crack, the chink. The fret. And he moved in.

“And yet, every other monk came with a discipline. For instance, I understand Frère Alexandre is getting old, perhaps too old to look after the animals. Wouldn’t it make more sense to find a replacement for him?”

“Are you questioning my judgment?”

“I certainly am. I’m questioning everything. Why did you recruit Frère Luc when all he could bring was his voice?”

“I judged that his voice was enough at this stage. As I said, he can be taught other things, like animal husbandry from Frère Alexandre, if he shows an aptitude for it. We’re fortunate now.”

“How so?”

“We don’t need to beg other monks to come. Younger monks are interested. That was one of the great gifts of the recording. We now have a choice. And when they arrive we can train them. An older monk can mentor a younger, as Frère Roland was mentored and learned the trade of upholstering.”

“Perhaps Frère Luc can learn it too,” said Gamache, and saw the abbot smile.

“That’s not a bad idea, Chief Inspector. Merci.”

Still, thought Gamache, it didn’t quite explain the volte-face the abbot had made in recruiting. From choosing skilled and trained men, to choosing a novice. With only one outstanding skill. His extraordinary voice.

Gamache stared at the plan on the table in front of them. There was something wrong with it. Some sense he had, like in the fun house. A slight queasiness when he looked at it.

“Is there just the one hidden room?” he asked, his finger hovering over the Chapter House.

“As far as I know. There’re always rumors of long-forgotten tunnels and vaults with treasure, but no one’s ever found them. At least, not that I know of.”