"Good," said Stevelman. "I have two tentative hypotheses, then." He turned to the colonel. "Should I state them now, Colonel Petersen?" "There's to be no secrecy aboard this ship, Doctor. I want every man and woman on the ship to know all the facts at all times." "Very well," the medic said. "I'd suggest the deaths were caused by some unknown virus--or, perhaps, by some virulent poison that occurred occasionally, a poisonous smog of some kind that had settled in the valley for a time and then dissipated." Wayne frowned and shook his head. Both hypotheses made sense. "Do you have any suggestions, Doctor?" Petersen said. "Since we don't have any direct information about why those men died, Colonel, I can't make any definite statements. But I can offer one bit of advice to everyone: _wear your suits and be alert_." * * * * * During the week that followed, several groups went out without suffering any ill effects. A short service was held for the eight of the _Mavis_ and then the skeletons were buried in the valley. They ran a check on the double-nucleus beryllium toward the end of the week, after it had been fairly safely established that no apparent harm was going to come to them. Wayne and Sherri were both in the crew that went outside to set up the detector. "You man the detector plate," said Major MacDougal, who was in charge of the group, turning to Wayne. He put his hand on the plate and waited for the guide coordinates to be set. MacDougal fumbled at the base of the detector for a moment, and the machine began picking up eloptic radiations. Wayne now looked down at the detector plate. "Here we are," he said. "The dial's oscillating between four and eight, all right. The stuff's here." MacDougal whistled gently. "It's really sending, isn't it!" He pointed toward the mountaintop. "From up there, too. It's going to be a nice climb. Okay, pack the detector up and let's get back inside." They entered the airlock and passed on into the ship. "The D-N beryllium up there, sir," Major MacDougal said. "It's going to be a devil of a job to get up to find the stuff." "That's what Captain Wayne's here for," Petersen said. "Captain, what do you think? Can you get up here?" "It would have been easier to bring along a helicopter," Wayne said wryly. "Pity the things don't fit into spaceships. But I think I can get up there. I'd like to try surveying the lay of the land, first. I want to know all the possible routes before I start climbing." "Good idea," Petersen said. "I'll send you out with three men to do some preliminary exploring. Boggs! Manetti! MacPherson! Suit up and get with it!" * * * * *