"Not bothersome, Sandrake. Impossible. Imagine going into a project giving about .000,37% yield for two hundred-fifty billion Telfans. The required dose of the antibody is forty-seven milligrams. Call it fifty, for round numbers, Sandrake, and you get a total figure of one trillion, two hundred-fifty billion milligrams, or one million two hundred fifty thousand kilograms. At four ten-thousandths of one percent yield, we'd have to process something like three hundred billion kilograms of raw material and then rectify it through that long and laborious process of fractional crystallization, partial electrolysis, and fractional distillation--with a final partial crystallization. Processing that much raw material would be a lifetime job at best. Doing it under pressure, with the planning and procurement problems intensified by the certainty of the few short weeks we have ... ah, Sandrake, it is impossible." "What is this trouble specifically?" "The final addition of silicon. It will not enter the compound, but forces something less active from the combination." "Making it useless?" "Right." "You've tried it?" "And it works," nodded Orfall. "And knowing that you of Terra have some wonders in science, we would like to know--" "You see," interrupted Orfall, "they've figured that the catalyst would be less than sixty-one percent efficient, if we could combine the silicon with it and let it replace into the other compound. That would work. But again we are stuck. The catalyst is stable as it is. What has Terra done to assist in forcing combination in unstable compounds?" "Must be something," said Sandra, thoughtfully. "May I have a moment to think?" "Certainly." "And one thing more. Haven't you anything that even resembles tobacco on this sterile planet?" "I'm afraid not," said Theodi. "Believe me, we have sought it." "Thanks," said Sandra. "I know it was for me. But, fellows, I think better with a cigarette." "We have analyzed the one you gave us, and haven't found a similar weed--" "O.K., I'll do my thinking in a higher plane," smiled Sandra. * * * * * A thought, fleeting as the touch of a moth's wing, crossed Sandra's mind. She fought to reclaim it. It had some association with an experience--some experience in which she had failed, somewhere. Recently? It might have been. Long ago? Sandra didn't think so. She sat there silent, and the Telfans left with a short statement to the effect that she might be able to think better alone. They would return later. It had to do with something highly scientific; something of a nature that staggered her imagination. It was coupled with something vast, something deep, something complex. Her eyes fastened on a spot of brilliant light, reflected from a polished and silvered glass vase at her bedside, and as she sat there with her eyes unseeing, deep in concentrated thought, her mind focused upon the one thing of vastness that she had been involved in.