"You'll remember," he told the intent Hawk, "that Ku Sui's men kidnapped me from our friend Kurgo's house in Porno. There were five of them: robot-coolies. They took us entirely by surprise, and killed Kurgo and bore me to Ku Sui's asteroid. "Well, I had come to Kurgo's house in the first place to arrange for supplies for building an addition to my laboratory, and I had with me a sheaf of papers containing plans for this addition. The plans are not important; they tell nothing--but there was a figure on one of the papers that might reveal everything! The figure 5,576.34. Do you know what that stands for?" The adventurer thought for a moment, then shook his head. Leithgow nodded. He went on: "Few would. _But among the few would be Ku Sui!_ "You'll remember that on building my laboratory we considered it extremely important to have it on the other side of the globe from Port o' Porno--diametrically opposite--so that the movements of our ships to and from it would be hidden from that pirate port. Diametrically opposite--remember? Well, the diameter of Satellite III is 3,550 miles. This diameter multiplied by 3.1416 gives 11,152.63 miles as the circumference, and one half the circumference is 5,576.34 miles--the exact distance of my laboratory from Port o' Porno!" "I see," Carse murmured. "I see." "That figure meant nothing to you, nor would it to the average person; but to a mathematician and astronomer--to Dr. Ku Sui--it would be a challenge! He would be studying the paper on which it is written down. One of Eliot Leithgow's papers. Plans for an addition to a laboratory. Therefore, Eliot Leithgow's laboratory. And then the figure: half the circumference of Satellite III. Why, he would at once deduce that it gave the precise location of my laboratory!" * * * * * The Hawk rose quickly. "If those papers fell into Dr. Ku's hands--" "He would know exactly where the laboratory is," Leithgow finished. "He would search. Its camouflage would not hold him long. And that would be the end of my laboratory--and us too, if we were caught inside." "Yes," snapped the Hawk. "You imply that the papers were left in Kurgo's house?" "I had them in the bottom drawer of the clothes-chest in the room I always use. The coolies did not take them. At that time they wanted nothing but me." Friday, rubbing his woolly crown, interjected: "But, even if Ku Sui's still alive, he wouldn't know about them papers. Far's _I_ can see, they're safe."