"Of course. Now, with one notable exception, all elements in this series were discovered during the Overgovernment's investigation of Riemann space properties in the two intragalactic creation areas we have mapped to date. As you may recall, that program was initiated forty-five years ago. The elements we're talking about are radioactive: half-life of up to an hour. It was suspected they had a connection with the very curious, apparently random distortions of space-time factors found in the creation areas, but their essential properties made it impossible to produce them in sufficient quantity for a sufficient length of time to conduct a meaningful examination. "Ymir, the last element of this series, was not discovered in the same areas, or at the same time. It was located ten years later, in stable trace-quantities in the asteroid belt you've mentioned, and to date it has not been found anywhere else. Ymir is a freak. It is chemically very similar to the rest of the series and has an unstable structure. Theoretically, its presence as and where it was found was an impossibility. But it was recognized eventually that Ymir produces a force field which inhibits radioactivity. Until the field is interfered with the element is stable...." "What interferes with it?" Camhorn grinned. "People. Until it's deliberately tampered with, Ymir is changeless--as far as we know. Furthermore it will, in compound, extend its inhibiting field effect instantaneously to three other elements of the same series. A very fortunate circumstance, because Ymir has been found only in minute amounts, and unknown factors still prevent its artificial production. The other three elements are produced readily, and since a very small proportion of Ymir retains them in stable--or pseudostable--form, they can be conserved indefinitely." "_That's_ the Ym-400 compound?" Fry asked. "That's it." Fry said thoughtfully, "Perhaps I should remind you, Howard, that this conversation is being recorded." Camhorn nodded. "That's all right. Now that we know someone else is in possession of sixty-eight kilograms of Ym-400, we're confronted with radically altered circumstances. The loss incurred by the theft isn't important in itself. The Ymir component in such a quantity is detectable almost only by its effects, and the other components can be produced at will. * * * * * "The question is how much the people who have the stolen compound in their hands actually know about it. We would prefer them to know several things. For example, up to a point Ym-400 is easily handled. It's a comparatively simple operation to reduce or restore the force field effect. The result is a controlled flow of radioactivity from the compound, or its cessation. Now, you've mentioned having heard that Ym-400 transmutes space-time stresses--" Fry nodded.