“Under the monastery.”

“Like a crypt?”

“Precisely! It was sealed off. The brothers installed a hole to feed the rats, but the crypt went deep enough to safely isolate them from the rest of the monastery. Thus protecting the animals and the monks.”

“And also preserving the plague,” she mutters. “Oh, my God!”

“What is it, Alana?”

“Don’t you see, Claudio? An enclosed ecosystem for rats who carried the plague but were immune to it themselves.”

“You do not think . . .”

“Yes. Yes, I do. The healthy rat Justine found was also carrying plague. She said it was different from any known breed. What if it was a direct descendant of those rats the monks buried under their church over six hundred years ago?” Her voice goes hoarse. “Claudio, what if the time for atonement is now?”

Alana bids a hasty goodbye to Claudio and hurries out of the isolation ward. Their discussion about the medieval monks reminds her of Juliet’s comment about the well-groomed “religious lunatic” that she and Lalia had encountered in Scampìa. As soon as she clears the decontamination station, she extracts her cell phone and dials Sergio. “The surveillance cameras, Sergio,” she says by way of greeting. “The ones mounted on the walls all over Scampìa.”

“What about them?”

“Can you get your hands on the footage?”

“All of it?”

“If need be, yes.”

“Even if we could, Alana,” he says, exasperation creeping into his tone, “the number of agents and hours it would take to go through all of that video . . .”

“So narrow it down. Can you check the footage on the day Juliet and her friend Lalia ran into that ‘religious lunatic’ she told us about? Juliet should be able to give you the approximate time and location.”

“Perhaps,” he says. “But Juliet’s story changes by the hour. The drugs . . .”

“I know, Sergio. Maybe it’s not related, but it can’t hurt to track down an image of this guy’s face. Figure out who he is and what he was doing there.”

Sergio is silent for a moment. “I will see what I can find out.”

After she hangs up, she tries Byron’s mobile number but only gets his voice mail again. She assumes he’s still tied up at City Hall.

Just as she reaches the automatic sliding door exit, Nico calls to her from behind. He jogs over and greets her with a kiss on both cheeks. His stubbled chin grazes her face. But his proximity and familiar scent have little of the previous impact.

“You disappeared, Alana,” he says.

She eases out of his embrace. “I was in Naples most of the day, Nico.”

“Yes, the new case. Tell me.”

“Cases.” She summarizes what she knows of the two new victims in Naples. “But there’s a breakthrough here in Genoa. It could be even more relevant.”

He frowns. “What is it?”

“The diary Claudio translated.”

“How is that related?”

Alana tells him about the medieval rats that were immune to the plague and how the monks sequestered them under the monastery in a subterranean sanctuary.