“They usually do, in bad times.” She thinks again of the slain Turkish teen. “Even today.”

“Pasqua himself, he was deeply involved.”

“In the scapegoating?”

“No, the contrary,” Claudio says. “Inevitably, Pasqua contracted the plague. He was nursed to health by another doctor and his family. A Jewish family. In those days, the Church was everything. And not very tolerant of outsiders, especially Jews.”

“I can imagine.”

“But for Pasqua it was personal. You see, he fell in love with his colleague’s daughter.” Claudio describes Pasqua’s relationship with the Jewish family, and how he struggled to protect them from deadly persecution. He pauses to look over his notes and then nods to himself. “There is one other big coincidence between his experience and ours.”

“What’s that?”

“Pasqua spent a lot of time at the San Giovanni Monastery.”

“The monastery again.” Alana shakes her head in surprise. “Why? What was he doing there?”

“At first he went to tend to the ill brothers.”

“What do you mean, at first?” she asks, sensing significance. “What changed?”

“This part is . . . what’s the expression . . . mind-blowing! When Pasqua fell sick himself, he went to San Giovanni to find antiserum.”

“Antiserum? In the 1300s?”

“It seems the clever monks had noticed that some of the rats inside the monastery had stopped dying. As if they were immune to the plague.”

“Immune?” The word runs through Alana as viscerally as an electric shock.

“Yes,” he says. “The monks, they viewed these rats as a sign from God. They worshipped them. Like the relics of some long-dead saint. The abbot, Don Marco, even had them build a pen and assigned a monk to watch over the rats. But the first few rat keepers—or the Custodi di ratti, as they referred to them—died from infection. You see, these rats were still contagious. So the monks built a special place to house them safely away from contact with the rest of the brothers.”

“The monks deliberately preserved infected rats?”

“Yes.”

“Why would they do that?”

“Two reasons. One, despite the deaths, Don Marco believed the presence of the rats offered the brothers a kind of paradoxical protection from the plague itself.”

Alana sits up straighter. “And the other reason?”

“To preserve the rats for the next time God needed to punish man for his sins. Or as Don Marco put it . . .” Claudio uses a finger to scroll down his laptop’s screen. “ ‘For when atonement is again required.’ ”

“Atonement? Jesus!” The hairs on her neck bristle. “These monks were storing the plague like an incubator in a lab? So it could be released again?”

“Yes, but they also might’ve been housing the cure,” Claudio points out. “When Pasqua became sick, he reasoned that if he drank the blood of these rats, he might get better, too. It apparently worked for him. You see? A primitive form of antiserum, no?”

Alana’s heart leaps in her throat. She’s not thinking of antiserum or curses. “Where did the monks build this rat sanctuary?”