“The Behavioral Sciences folks don’t think so,” Thornton said. “They’ve talked to a lot of Novak’s neighbors. He was energetic and positive. The guy walked a mile or two every day; hell, he was playing tennis until a couple years ago. Only reason nobody was worried about not seeing him lately was because of the cold weather. They figured he’d come back out once it warmed up. You saw all those espionage books on his desk. I think he was on the trail of a spy, and I think that’s why somebody fed him a pellet of iridium-192.”
“I can’t figure out how they did it,” I said. “It must not have been hidden in a hunk of meat or cheese. He’d have broken a tooth or at least spit the thing out.”
“I’ve been thinking about that,” Thornton said. “If you’re a health-conscious old guy, what do you swallow a lot of every day?”
“Ex-Lax,” said Emert, drawing a laugh from everyone.
“Pills,” I said. “Vitamins.”
“Exactly,” said Thornton. He turned to Emert. “Remember the medicine cabinet?”
“Looked like a damn pharmacy,” said Emert. “Mostly nonprescription stuff, though. Super-omega-this and antioxidant-that and mega-ultra-prostate formula. Flaxseed and glucosamine and St. John’s wort and I don’t know what-all else. The old dude was scarfing down twenty, thirty horse pills a day.”
“The iridium source,” I said. “How big was it?”
“Not very,” said Thornton. “About an eighth of an inch in diameter. Plenty small enough to slip inside one of those capsules. I bet if we go back and look at all those bottles, we’ll find a pill bottle that doesn’t have as many fingerprints as the rest.”
“Because somebody wiped it clean after hiding the pellet inside the capsule,” said Emert.
Thornton nodded, then shifted back to the rad lab’s findings. “The half-life of iridium-192 is only seventy-four days,” he said. “So seventy-four days before the incident in the morgue, the pellet—assuming it was irradiated and fabricated that long ago—was twice that hot: nearly two hundred curies.”
“I’m assuming this thing wasn’t pried out of a household smoke detector,” said Emert.
“Not a chance,” said Thornton. “Smoke detectors use a different isotope, americium-241, and they use tiny, tiny amounts. Like a microcurie.”
“A microcurie,” the detective said. “That’s, what, a thousandth of a curie?”
Thornton shook his head. “A millionth,” he said. “A smoke detector contains one-millionth of a curie of radioactivity, and it’s mostly alpha radiation, the kind that can’t penetrate your skin or even a piece of paper. This iridium source in Novak’s gut was a hundred million times hotter, and it was spewing gamma, which can shoot through several inches of steel and come out the other side still feeling frisky.”
“What about a TheraSeed,” said Emert, “those little radioactive pellets they put in the prostates of old farts like me to shrink tumors?”
“Those are tiny,” Thornton said. “Small enough to be injected through a syringe. And they’re generally palladium-103 or iodine-125. They’re also very, very weak compared to this. You wouldn’t want your prostate to get cooked like Novak’s gut, would you?” Emert shuddered. “Speaking of medical isotopes, though,” Thornton went on, holding up an index finger to indicate that he found this an interesting sidelight, “one of the uses of iridium-192 is to create medical isotopes like palladium and iodine.” I was losing track of all the isotopes, but Thornton seemed to have no trouble keeping them straight.
“One isotope creating another,” I said. “The atomic ripple effect?”
“More like billiard balls,” Thornton said. “All those protons and neutrons and electrons and photons ricocheting around on the pool table of the universe. I’m amazed everything hangs together as well as it does. One of these days, seems like, the cosmic cue stick will strike, all the balls will scatter, and then they’ll drop, one after another, into the corner pockets and side pockets of oblivion.”
“Why, Agent Thornton,” I said, “you’re a poet.”
He laughed. “Nah, it’s just smoke and mirrors. I’m desperately trying to distract you from the realization that I don’t really understand this stuff.”
Smart, poetic, and self-deprecating, to boot—no wonder Miranda seemed to be taking a shine to him. “So this iridium-192,” I said. “UT Hospital has a pretty big nuclear-medicine department. Is there any chance this iridium-192 might have come from there?”
“Yes they are, but no it couldn’t,” he said. “They do create radioisotopes there. They’ve got a cyclotron right above the morgue that Ernest Lawrence would’ve given his left nut for. But UT doesn’t use iridium-192 sources.”
“Then who does?” Emert and I asked the question at the same time.