“No doubt, but this has to be a major conspiracy. You know what this stuff is used for? They use it to make firing mechanisms for nuclear weapons. No one admits to making it, although the major source is supposed to be Russia. I just read about it two minutes ago. So the FSB can just call someone and get it. But how do you get it in New York City? There has to be a lot of people involved. Serious people with access to this material. And I believe those guys when they warned me not to go to the police. I’m not going to the authorities till I have enough proof to go to the media at the same time.”

“The media?”

“I told you, I don’t trust ‘the authorities.’ ” Pia made quote marks in the air with her fingers. “If I give this story to the newspapers, whoever is involved won’t be able to bury it.”

“So what proof do you need?”

Pia turned back to the computer and made another search.

“Okay! Polonium-210 has a half-life of a hundred and thirty-eight days, meaning that it takes a hundred and thirty-eight days for it to lose half of its radioactivity. So if that’s what they used, there has to be some trace around someplace, either in the lab or in the rooms Rothman and Yamamoto occupied in the hospital. Even if someone was very careful giving it to them, there’s bound to be some residue just like there was in London in 2006.”

George joined Pia at the computer, looking over her shoulder. “How is polonium detected?”

“Here it is,” Pia said, pointing at the screen. “Alpha particles can be detected with a Geiger counter. Pretty simple.”

“Where are we going to get a Geiger counter?” George said. “Oh, let’s use mine. It should be in the bottom drawer on your right.”

“Very funny,” Pia said. “Geiger counters are not all that uncommon, especially around a medical center like this. They must have them in Nuclear Medicine. We’ll go over there and see if we can’t borrow one.”

“I couldn’t help notice that you said ‘we,’ ” George said. “So is this a formal invitation?”

“Of course it is,” Pia replied.

“Well, thank you,” George said. Actually there was no way he would have allowed Pia to go over to the hospital without him. He reached out and felt along Pia’s jaw. “Maybe we should get you X-rayed while we’re there. I know a technician who would do it as a favor.”

Pia pushed his hand away. “I don’t want to take the risk.”

“All right, here’s the plan,” George said. “I’ll help you look for a Geiger counter, but first I have to talk to my resident and come up with an excuse for not being around.”