"It was the only form of energy that hadn't been tried," I said, with a shrug. "Self-energy. Back on Earth, you ran that disc of parabolite through a hot atomic pile, and it became intensely radioactive, since the deadly emanations of the pile are even less than subatomic, and have no dimensions. Then a shielding coating of nullifying gamma plasm, the same stuff we use to keep our rocket chambers from dosing the passengers with deadly rays, and neat nickel plate over that. Emboss it with the seal of the World President, lacquer it in the colors of IS, and you have a neat, but incredibly potent, little fission bomb."
"And how could I set this off?" Baxter sneered. "Aren't you forgetting that the parabolite's at less than a critical mass?"
"Same way the old H-bomb worked," I said. "Under the gamma plasm, beside the radioactive parabolite, you have an atomic bullet, the kind the foot soldiers used in the Third World War. As for tracking it and detonating it, you must have a refinement of the tracking stuff you had in that blouse of mine. As the old H-bomb was triggered by an atomic bomb, so the parabolite, even at less than critical mass, could be triggered by the remotely-detonated atomic bullet. You planned to blow up the Ancients, and me with them, Baxter. Then you could go ahead and set off similar bombs, one each on Venus, Earth and Mars. The fallout would stay with the planets forever, even after losing its potency. And you could teleport your agents anywhere you chose."
"And the Ancients?" said Baxter.
"They reasoned out your intentions when you made that chunk of parabolite radioactive. Why do that unless you intended detonating it? But the very act of making it fissionable somehow took the teleportation-whammy out of it. They couldn't use it to snatch you, even when you were near it. Probably, since it seems the only likely reason, they couldn't use it because it was too atomically hot for them to work with." I was finished. I waited.
"Mister Delvin," said Baxter, after a long moment. "What do you intend to do, now?"
"Keep you in cuffs," I said. "Send an emergency call to the World Congress. See you corked into one of your own granite cells. With the air supply turned on, however. Though I wouldn't mind you having an hour or two of what I went through the other night."
"And," Baxter turned his head and nodded toward the handbag on the desk, "what about her?"
"She was being held conditional to my removing you as a menace," I said. "Consider yourself removed."
Baxter smiled. "And if the Ancients are not satisfied? What if they still desire my death, not simply my imprisonment?"