Fourteen women and six men had survived the thirty-march journey of the Hard Trek—so far. Accident and fatigue still took their toll, and the chimera still stalked the group, though it seldom had a chance to strike any more. They were farther away from the surface than ever—and between them and final escape still waited the nemesis that had driven Bedside mad.

The march ended. They camped huddled together, trying to protect themselves from the ominous gathering of unknown forces. These caverns were menacing.

“How much more?” a woman demanded, her voice too sharp, addressing herself to the sinister passages. Aton agreed: what other pressures would be brought to bear before Chthon let them go?

A shout. It was the voice of one of the women on scout duty. Teams always went out on prowl, now, while the main group rested. The chimera never attacked an alert formation.

The others gathered around. It was one of Bedside’s cairns, with a message scratched on the floor. The rock was soft, here, and could be decorated readily.

“What does it mean?”

It was the typical skull illustration of danger, but without the crossbones. A single word was underneath.

Aton spelled out the crude letters: MYXO. “Must be a medical term,” he said.

“Myxo,” Bossman muttered. “Don’t mean anything to me. Ain’t like him to leave his picture unfinished.”

“Either something drove him off—” a woman suggested.

“Or there’s a Myxo ’round here that don’t quite kill,” another finished.

They stood in a circle, looking at each other. No one knew. But one thing experience had made plain: Doc Bedside’s humor was scant, and his warnings were not to be ignored.

“We better move on fast,” Bossman decided. They were tired, but there was no dissent. There was danger here.

Fifteen minutes later a woman fell, clutching at her throat and head. No animal had attacked her, and nothing was wrong—visibly.

They halted for a brief consultation. Life was more precious at this juncture. If many more were lost, the party would be too small to win through the remaining challenges. There had to be scouting parties, guards, and reliefs for these, as well as individuals for special assignments for unpleasant work. Once the disciplined system broke down, the demise of the remainder would accelerate. Concern for the laggards was something new—but necessary.

They camped and made the woman comfortable. She was examined closely. What was the matter with her?

Her breathing was labored, rasping. Gradually her skin whitened. A slimy mucus was exuded all along her body, and a stomach-twisting odor arose from it. She had fallen prey to a disease—the first disease known in Chthon.

“We better kill her now,” a woman urged, “Before it spreads.”

Bossman considered the matter.

“Why bother?” Aton said. “We’ve all been exposed by this time.”

“How did she catch it?”

“I ain’t seen nothing like this before.”