“Red mercury doesn’t exist,” Len agreed, nodding emphatically. “You’re right, it’s a scam. But. Hmm. If it did exist, what might it be?” He raised a hand and began checking off digits. “It wouldn’t be a ballotechnic explosive. It wouldn’t be a room-temperature superconductor. It wouldn’t be a dessert topping and a floor wax. It wouldn’t be red. But. But. Suppose the Soviets had taken NAIL SPIKE at face value and began looking for the mysterious Ingredient X that was missing from the faked-up documents we leaked to them. Charlie, have you heard of induced gamma emission from nuclear isomers?”

“What, are we talking hafnium, now? I thought that was a bust, wasn’t it?”

Nuclear isomers are isotopes of some heavier elements that can exist for prolonged periods in an unstable high-energy state. Hafnium got a lot of airtime a few years ago because of a theory that you could use it to store gamma radiation and then trigger its release by hitting a block of the metal with gamma rays—making it a kind of nuclear battery, with an energy density millions of times higher than any chemical battery could achieve.

“We’re not talking hafnium,” said Len, “we’re talking mercury. Specifically, we’re talking red mercury. Which doesn’t exist. But if it did, it might be a metastable nuclear isomer of mercury that had been irradiated in a reactor for months, and that could be stimulated to discharge all its absorbed energy in a matter of milliseconds by hitting it with hard X-rays.”

“You’re shitting me!”