"Listen!"

Captain Strong grabbed the young master sergeant by the arm and stood stock-still in the swirling methane ammonia gas, his eyes searching the misty sky.

"What is it, sir?" asked Morgan.

"A spaceship decelerating," said Strong, "coming in for a touchdown!"

"I think I hear it now, sir!" said Morgan.

"Can you figure out where it is? I can't see a blasted thing."

"Sounds to me as though it's to the left, sir."

"O.K., let's go and investigate," said Strong. "There isn't any good reason for a ship coming down in this deadly soup—or in this area."

Walking slowly and cautiously, the two spacemen angled to the left, peering through the clouds of gas that seemed to get thicker as they moved along. The roaring blast of the ship became louder.

Strong put his hand out to stop Morgan. "Let's hold up a minute, Sergeant," he said. "I don't want to get too close until I know what we're facing."

They stood absolutely still, the gas swirling around them in undulating clouds that grew thicker one minute and then thinned out again. As the gas thinned for a few seconds, Strong gasped and pointed.

"Look!" he cried. "By the craters of Luna, it's Brett's ship!"

"Brett?" asked Morgan.

"Charles Brett. He owns that ship. It's the one that won the space race from Earth. Now, what would he be doing landing out here?"

"I think he came down beside that warehouse up ahead, sir," said Morgan, as the gas cloud closed in again, cutting off their view of the actual landing. "It used to be a storehouse for mining gear a couple of years ago, but it's been empty for some time."

"I think we'd better check this, Sergeant," said Strong firmly. "Come on."

Strong started forward, then stopped, as a particularly heavy cloud of the deadly gas swirled around them. The two spacemen clung together blinded by the dense methane ammonia that would kill them in thirty seconds should their oxygen masks fail. In a moment the foggy death thinned out again and they continued toward the warehouse and the sleek black ship behind it.

Tom Corbett and Astro heard the roaring blast of the ship's exhaust. They saw Brett and Miles haul the instruments out of the cavern. They saw; they could hear; but they could not move. For nearly three hours they had remained alone in the cavern, frozen in the exact position they were in when Quent Miles had blasted them with his paralo-ray gun. And then Brett and Miles were standing before them again, Miles covering them with his paralo-ray gun.

"Why should we break our backs loading the ship?" sneered Miles. "Let them carry it out for us."

"Look!" Strong cried. "It's Brett's ship!"

"All right, release them," agreed Brett. "But get that stuff loaded in a hurry. Walters is either getting suspicious or he's pulling a bluff. We can't take any more chances."

Miles flipped on the neutralizer switch of the paralo ray and leveled it at Tom. "We'll take the little fella first," he said. "If he acts up, we'll just leave the other fella the way he is."

He fired at Tom, and the young cadet began to shudder violently. His teeth chattered and he found it difficult to focus his eyes as his nervous system tried to shake off the effects of the ray. He crumpled to a heap on the balcony floor and gasped for breath.

"He won't be much use to you for a while." Brett laughed. "Look at him flopping around like a fish out of water."

"Get up!" snarled Miles at Tom, quickly flipping the ray gun back to positive charge. "Come on. You're not that bad off. Get up." He leaned over and prodded the cadet with the gun. "If you don't get up, I'll freeze you again," he threatened.

Tom struggled to his feet. "I'll get you for this, Miles," he gasped weakly, his teeth still chattering.

"Never mind the hot air!" snarled Brett. "Go down there and start hauling up those boxes."

Tom turned helplessly and stumbled down the stairs to the floor of the cavern.

"Now for the big fellow," said Miles. He fired the neutralizer charge and Astro started to quiver at the shock of the release. But he clamped his teeth together and made a quick lunge for Miles, reaching for the spaceman's throat. Expecting the attack, Miles stepped aside quickly and brought the gun down sharply on the big cadet's head. Astro dropped to the floor, half-stunned. The black-clad spaceman leveled the ray gun and sneered, "Try that again, you overgrown punk, and I'll drop you on your head."

Astro shook his head and stumbled to his feet. He glared at Miles, spun away, and walked down the stairs shakily.

Miles and Brett stood on the balcony and watched the two cadets working on the cavern floor. "Hurry it up there!" shouted Miles. "We haven't got all day."

Brett took his ray gun from his belt and stepped forward. "I'll handle Corbett," he said. "You take care of the big one."

"Right," replied Miles. "But stay well in back of them and keep your gun on them all the time."

"How long do you think it'll take to get the ship loaded?" asked Brett.

"Couple of hours. But what are you going to do about Walters if he's wise?" Miles shrugged his shoulders.

"Simple," said Brett. "We take the stuff we've got, haul it to the hide-out, dump it, and return to Atom City. Then we just sit tight and wait until the situation clears up here on Titan."

"What about that investigation?" asked Miles, keeping his eyes on the cadets, who were now staggering back to the stairs, each carrying a heavy lead box containing the precious uranium pitchblende.

"What can an investigation prove?" snorted Brett.

"I don't know. Walters and Strong are pretty smart cookies."

"Unless they have witnesses that you were messing around Kit Barnard's ship, which they don't, and unless they find out about Ross, which they won't, there isn't anything they can do."

Miles looked down at the shorter man beside him. "Ross, eh?" He laughed.

Brett stared at him and then shrugged. "I always get mixed up," he said. "But you know what I mean."

"Sure, I know." Miles turned to watch Astro and Tom start up the stairs to the balcony, the lead boxes on their shoulders. "What are you going to do with them?" he said.

"Take them to the hide-out and decide later. Besides, they'll be handy for unloading the ship."

"Good idea," nodded Miles. He took a deep breath and smiled. "I sure wish I could see Walters' face when he learns about the new load of uranium that'll flood the market."

Brett laughed. "Yeah, and with the customs clearance we'll get to haul in the crystal, there'll be no way they can figure out how it's getting in."

Miles turned and shouted at the two cadets struggling up the stairs. "Come on, you two. Get a move on."

"We're making it as fast as we can, Miles," Astro protested.

"It ain't fast enough," sneered the spaceman. He reached out with his free hand and slapped Astro across the mouth. "That's just to remind you to watch your tongue, or you might wind up an icicle again."

Astro dropped the box and crouched, his big frame ready to be released like a coiled spring. Miles backed up and fingered the trigger on the ray gun. "Come on, stupid," he snarled. "Come on, I'll give it to you again, only this time—" He smiled.

"No, Astro," called Tom. "There's nothing we can do now. No use getting frozen again."

"That's using your head, Corbett." Miles laughed. "Pick up that box and get going."

Astro picked up the lead box again and staggered after Tom toward the door. Miles and Brett stepped back, guns ready, and watched the two cadets walk slowly ahead of them into the tunnel.

Captain Strong and Sergeant Morgan crept to the side of the warehouse and flattened themselves against the wall. With the gas swirling around them thicker than ever, they found it more difficult than ever to see where they were going.

"I think I see a door ahead," said Strong.

"Want me to see if it'll open, sir?" asked Morgan.

"No. I'll look around in the warehouse," replied the Solar Guard captain. "You investigate the ship. If anyone's aboard, keep him there until I contact you. If not, come back here and wait for me."

"Very well, sir," said Morgan, and turned toward the black ship. In a moment he was lost in the deadly mist.

Strong made his way to the door and twisted the latch. The door slid open easily, and he stepped inside, closing it behind him and waiting for some signs of life or movement. The gas was like a thick fog in the room and he inched his way forward, hands outstretched like a blind person. Gradually he began to see the vague form of a door on the opposite wall and he made his way toward it, completely unaware that he came within inches of falling through the open trap door in the floor.

He opened the door in the wall slowly, peering inside cautiously. He was startled to feel the faint rush of air on his hands and to see the room clear of the dangerous methane ammonia gas. He moved quickly inside and made a hurried inspection of the gear, not bothering to look to examine it closely. He shrugged his shoulders. It was just as Morgan had said. An abandoned warehouse with old mining gear and nothing else.

Suddenly he stopped. There was something strange about the room and he looked around again. The gas! There were no ammonia vapors in the room. He quickly searched along the walls for some outlet of oxygen, remembering now the rush of air he had felt as he opened the door. Close to a corner near the door, he found a small opening. Air poured out of it in a steady rush. He straightened up, his face grim. "So that's it," he said to himself. "Somebody has been sucking off oxygen from the main pumps!"

Strong headed for the door. "But why?" he asked himself. "Why in this particular building?"

He strode out of the room and inched his way across the outer room toward the front door, again narrowly missing the open trap door.

Once outside, he made his way along the side of the building in the direction that Morgan had taken. When he reached the corner, he could see the black bulk of the Space Knight a hundred yards away. He ran toward the base of the ship and met Morgan coming toward him.

"Find anything, Sergeant?" he called.

"Nothing, sir," replied Morgan. "The ship is ready to blast off and her cargo holds are full. But that's all."

"Full of what?"

"I couldn't see, sir. The main hatch was locked and I could only see through the viewport. But it just looked like general cargo to me."

"Couldn't have been crystal?"

"It might have been, sir. It was pretty dark in the hold but it looked like a lot of boxes to me."

"You don't put crystal blocks in boxes," said Strong.

"Sometimes they do, sir. The more expensive grades are crated, so that the surfaces won't get scratched. Pieces that are going to be used for outer facings on a building, for instance."

"All right, Sergeant. But I found something back in that building that is going to prove very interesting."

"The cadets, sir?"

"No. An illegal use of oxygen!"

Quickly Strong explained his discovery, concluding, "Come on. We're going back in there for a closer inspection!"

"But we can't, sir," said Morgan.

"Why not?"

"We only have enough oxygen left in our tanks to get us back to the cleared area."

"Blast it!" growled Strong. "Aren't there any masks aboard the ship?"

"No, sir," replied Morgan.

"Very well, then. The only thing we can do is go back and bring out a searching party in force." Strong turned and walked rapidly away. "Come on, Sergeant, I think we're on the way to answering a lot of questions about the failure of the screens."

Almost running, the two spacemen disappeared into the swirling mist of deadly gases.

No sooner were they out of sight than Tom Corbett and Astro, faces covered with oxygen masks, emerged from the warehouse and headed toward the ship, Miles and Brett close behind them with paralo-ray guns leveled at their backs.