faster than I can kill them. Now I’ve got about eight rounds of ammunition left—no, nine, I see.” He showed an old-fashioned pistol.

“But the camera crew will search for us.”

“A tiny valley in three hundred miles of mountains? And your friends won’t know where to look, from what you say? For all they know, you might have crashed anywhere on Titan.”

He hesitated.

“I’d forgotten something. You’ve got to be inoculated immediately. Otherwise you’ll just go crazy and die.”

Kathleen blinked. “Huh?”

“The plague—the one you say killed that man Udell and his crew. It nearly killed us before the Kestrel’s doctor got on the track. You’ve got the virus in you now.”

“That’s impossible,” the girl said. “Unless we were infected since we cracked up.”

“You were infected before you ever landed on Titan,” Sherman said grimly. “The virus is a protein molecule that exists in living organisms—Zonals and humans alike. Usually it’s harmless—a recessive characteristic. But under the influence of a certain kind of radiation the virus becomes actively malignant.”

“I don’t get it.”

Sherman had talked a good deal with the Kestrel’s doctor before the latter died. He told Kathleen about the tobacco mosaic disease—how a plant, suffering from common mosaic disease, may suddenly become victim of a more virulent form—acuba—caused when the basic molecules change their structure.

“It’s like that,” he said. “There’s a meteor on this continent which emits rays that develop the latent, harmless virus in one into the active, malignant form. That’s what originally wrecked the minds of the Zonals, you know.” He noticed Kathleen’s pallor.

“Don’t worry too much about it. I’m still alive, you see. Our doctor worked out a cure. The Zonals have antibodies in their bloodstreams—antibodies strong enough to immunize a human. They developed ’em, but not in time to save themselves from degeneration. I prepared a fresh batch of serum yesterday—so come along and I’ll inoculate you.”

“But—will Tony—”

“He’ll be safe here. The Zonals don’t dare come into my castle.”

Kathleen followed Sherman through another of 

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