something I would like to know, though. Grossman told us the soil killed humans. I wonder how they die?"

"I can answer that. Daddy told me the first day I was here. He was warning me against ever leaving the shielded areas ... the Fort, the city, the roads. He said that if they wander onto the soil of Titan without protection, humans just shrivel up and crumble into dust like—like mummies!"

"Like mummies, eh!" grunted Rocky. He sounded quite well satisfied. "Mmm-hmm! Then that fits, too. Yes, I think I'm beginning to understand a lot of things ... including the reason Factor Grossman would like to rid this little world of all competitors—"

"Well, don't keep secrets!" snapped Bud. "We'd like to know, too. What's it all about?"

"No time now. There's the hill out yonder. Pull up here, Miss Lynn. Here's where we leave you."

Lynn stopped the roller obediently. But as Bud and Rocky climbed out she asked, "What do you want me to do now? Can't I come with you?"

"No. You turn the roller around and wait here. We have no idea what we're going to buck up against. We may have to retreat—suddenly. If so, I'll fire three blasts on my Haemholtz. Two short, one long. If you see that signal, get ready to start moving. We'll come on the double-quick. But if we're being pursued too closely to make it—"

"Yes?"

"Then don't wait for us!" ordered Rocky.

"Head for the Base and bring the Patrolmen. Understand?"

"All but one thing," complained the girl. "Why not send for a platoon of Patrolmen right now? Why wait until it is too late?"

"Because," explained Rocky patiently, "despite our suspicions, we have as yet no actual proof that the factor is involved in anything shady. The Patrol is an organization sworn to maintain the Law, not to violate it, riding roughshod over the rights and privileges of citizens.

"When we are certain—as I fully expect we shall be shortly—that Grossman is implicated in some illegal scheme then we can call in the Patrol. But until that time—"

"Until that time," broke in an oily, taunting voice, "you will play the part of quixotic fools, eh, my dear Doctor? But has it never occurred to you that by the 

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