age, intricate defenses and hidden underground
entrances; had, indeed, hidden it so well that none of the scavengers
and brigands and more personal enemies who infested Port o' Porno
remotely suspected that his headquarters was on the satellite at all.
Ships, men, could pass over it a score of times with never an inkling
that it lay below.

After a short silence, Eliot Leithgow began his explanation.

"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 th