they produce on the opposite side of the ship a series of overlapping images. You can look at the ship from any direction and you will see only a composite, naturally colored image of whatever happens to be directly behind it. This image fills in a faithful reproduction of that portion of the surroundings which normally would be obscured by the hull, and the craft itself becomes completely invisible."
"Now I comprehend," Mayer said. "But does it actually work?"
"Of course it works, you Goop," Sullivan snorted. "You don't suppose I'd install a device like that on the Cosmicraft without first testing it very thoroughly do you?"
"Excuse me for asking," Mayer apologized.
"Oh, that's A. Z., kid. As a matter of fact, the scheme doesn't work as well as I'd like it to," Sullivan amended this previous statement. "When you get up really close to it, the illusion is far from perfect. However, at a distance of twenty-five meters or more it functions very satisfactorily. And, since it is extremely unlikely that anyone will come any closer to us than that while we are hiding on Mars, it ought to serve—"
He was interrupted by Captain Brink, who said quietly: "Excuse me for cutting into this learned dissertation, Jimmy, but don't you think you had better get ready to land."
"A. Z., Chief," Sullivan grinned.
CHAPTER V
Into the Weasel's Lair
WITH that uncanny skill which comes only from many years of experience as a space navigator, Captain Brink set the Cosmicraft down in the Martian desert of Menfol, about half a kilometer from the sinister fester of shacks which constituted Zurek's nest of blackguards.
After a brief conference it was decided that Sullivan, who understood the Martian language perfectly, should steal into Zurek's village and endeavor to find out what had happened to the slaves who had recently been captured in Ganymede.
As he was about to depart, Captain Brink said: "Just a minute, Jim. After you have completed your intelligence job, how are you going to find your way back to the Cosmicraft?"
"Zee!" Sullivan exclaimed. "Glad you reminded me of that! I'd have a sour time, wouldn't I, hunting all over Mars for an invisible spaceship."
"Why not use a thread?" Mayer suggested.
"A thread? I'm afraid I don't integrate with you."
"Don't you remember the yarn—"
Before he could go any further, Sullivan interrupted him with: "Yarn? I thought you said thread."
"I did, you goop. I got the idea from a yarn I read about a mythological hero who found his way out of a maze by unwinding a spool of thread."
"Now that's a sizzling idea," Sullivan sniffed. "The only trouble is that we don't happen to have any thread aboard—unless you took your sewing basket along."
"You might use wire instead of thread," Mayer persisted.
"Yes. I might if we had a few hundred meters of wire. Any amount under half a kilometer would be worthless for the purpose. I suppose your next suggestion will be that I scatter bread crumbs along the trail like Hans and Gretel did in the ancient fairy tale."
