“How could they let that happen? Like losing track of a nuclear bomb. Alana, if this outbreak is related to that . . .”

He doesn’t need to finish the sentence. She has harbored the fear since the moment she first laid eyes on the dying Vittoria. “Did you ever hear how the plague reached Europe during the Middle Ages?”

“What do the Middle Ages have to do with biological warfare?”

“Caffa.”

“What is Caffa?”

“A port in the Ukraine. On the Black Sea. Now known as Feodosiya. But in the fourteenth century, Caffa was the key trading port between East and West. And you’ll never guess which great merchant seafaring state colonized Caffa at the time.”

“Genoa?”

She nods. “In 1347, the Mongols laid siege to the walls of Caffa. They probably would have made short work of it, too, if the plague hadn’t swept in from Asia around the same time. The Mongols died off in droves. They assumed the Genoese inside the fort were somehow responsible. So—in maybe the first-ever documented example of biological warfare—the Mongols began to catapult rotting corpses of their own soldiers over the walls of Caffa. Soon the Genoese became sick, too. It caused mass panic, and many of them fled for home.”

“Bringing the plague back to Europe with them?”

“Exactly. Via the so-called plague ships,” she says. “To Sicily, to Venice, and eventually, of course, right here to Genoa.”

They lapse into a despondent silence. Alana feels her phone vibrate. Relieved for the distraction, she reaches for it. Her pulse picks up as soon as she recognizes the cell number for Emilio’s. The text reads: “Via Capodistria e Via Vincenzo Bellini. Un’ora.”

Alana turns the screen out to show Nico. “Emilio wants to meet!”

He nods. “In one hour. I know that neighborhood. Cornigliano. I will take you.”

“Should we let Byron know?”

“Byron has more than enough on his hands.”

Alana vacillates a moment. If they arrive with too many people, Emilio may not show or might be too spooked to talk. She replies to Emilio’s text with one word: “Sì.”

Nico drives, but with less urgency than on their last frantic ride. Alana’s phone rings, and when she sees Byron’s name on the call display, she answers on speakerphone.

“Where are you?” Byron demands.

She glances at Nico, who shakes his head. “Tied up. NATO business.”

“Nice to know NATO has more pressing priorities when all hell is breaking loose around here.”

“What happened?”

“Multiple new patients. Worse, there are two cases on the other side of the city that are definitely the bubonic plague. Neither have any connection to Vittoria Fornero or Sonia Poletti. We can’t even say for certain that Vittoria is Patient Zero anymore.”

“For this to be spreading through the skin, not the lungs . . .”

“There has to be some kind of animal reservoir. It must be incubating among rats or other rodents before being transmitted by fleas.”