Walking leisurely to the second set of pumps, Greg replied, "Plenty of time. And then we'll do the recycling system, just to make certain." He laughed again. "That'll be our own little bit of redundancy."

He slapped the big wrench on one of the nuts holding down the main pump's domed top. It made a beautiful, echoing clang.

"We won't pass out before the job's finished, will we?" Melissa asked. She worried that Greg would screw up, one way or another. They were so close to the final ending, she didn't want to go through this and then find that they had failed.

"No," Greg assured her. "This chamber is sealed off from all the others. There's enough air in here for the two of us for days on end."

"But how will we...?"

"Finish it?" Greg's smile beamed at her. He moved closer to her, whispering like a little boy, "When all the pumps are done, when I've knocked out the recycling system, I'll open the hatch out into the tunnel. Our air will blow out and we'll be dead in a couple of minutes."

"You're sure?"

"As certain as death can be," Greg said.

Melissa kissed him on the lips. "Then let's make love while the air goes out. Let's die in each other's arms."

Greg cocked his head slightly. "Sure. Why not?" She sighed. It would all be over soon. What was it Shakespeare said? All the heartache and the thousand natural shocks flesh is heir to. It's all going to end, and Moonbase and nanotechnology with it. She felt a peace and contentment that she had not known since childhood.

"Stop daydreaming and help me with this," Greg snapped.

Startled, she looked at the man she hated, the man she loved, and went to help him.

A dull booming sound reverberated through the shadowy, high-ceilinged cave.

"What was that?" Melissa asked.

Greg peered up into the shadows. "I don't know."

Another, like the growl of distant thunder.

"They're trying to get in again!"

"No," said Greg. "It's not the hatch. It's too far away, whatever it is."

Melissa thought wildly. "Maybe they're launching a ship, getting away!"

Greg shook his head angrily. "There's only one LTV on the pads and it can only hold a half-dozen passengers, max."

"Your mother-"

"My mother wouldn't even think of trying to get away," Greg said. "It wouldn't even enter her mind. Or Doug's, they'll try to figure out some way to save everybody, whole base."

"You're sure?"

"Positive. Especially Doug. He'll want to be a hero. He'd rather die than let Moonbase be destroyed. Even if he was safe in bed in Savannah, once we wipe out Moonbase he'll die too."

"You're sure?" Melissa repeated.

Greg laughed bitterly. "That noise is probably Doug battering his thick skull against the airlock hatch, trying to ram his way in here."

VACUUM VENT NO. 3A.

"When all else fails," granted Brudnoy, "use the precision adjuster."

He and Doug gripped the long metal rod they had scavenged from the construction spares supply and rammed it again into the square metal ceiling panel that was the access to the vacuum vent that ran the length of tunnel three. The booming thud reverberated hollowly down the length of the tunnel.

"Well," Doug panted, "I don't think we're going to surprise them."

Brudnoy peered up at the access panel. It had barely budged. "I don't know about that," he said, wiping sweat from his eyes with the back of his sleeve. "They may hear the noise we're making, but will they know what's causing it?"

"Maybe not," Doug agreed half-heartedly. He gripped the rod again in both hands. "Come on, let's get it done."

We're not moving fast enough, Doug told himself. Greg's in there taking the EVC apart and we're stuck here as if we're glued to the floor.

For one of the rare times in his young life Doug felt real anger. He wants to kill us all, kill himself and me and Mom and everybody. He wants to kill Moonbase. He wants to kill my father all over again.

Never! he snarled inwardly. I won't let him get away with it He rammed the rod with all his strength against the unyielding ceiling panel.

Four more bangs and the panel gave way with a groan. Doug could see it lift away slightly from the lip of the square in the rock ceiling.

"I think that did it," he said, puffing from the exertion.

"Yes." Brudnoy was panting, too. Wheezing.

"Okay," said Doug. "You'd better get back to the control center and tell them I'm on my way."

"But I'm going with you," said Brudnoy.

"No," Doug said, placing a hand on the Russian's bony shoulder. "This is something I have to do alone. Besides, I need you to take care of my mother."

Brudnoy gave him an odd look. Then he shrugged submissively. "I understand. I'm too old for heroics."

Doug smiled at him sadly. "You're out of shape, you know."

Shrugging, Brudnoy replied, "Too much soft living. Here, at least I can help you up."

"I can jump it. Get on back before he starts pumping the air out of this tunnel, too."

"They can't," Brudnoy countered, "now that the hatches have all been closed."

Doug nodded. "Yeah, all he can do is knock out the pumps or the recycling system and let us strangle slowly."

"It's always best to look on the bright side," said Brudnoy.

With a rueful grin, Doug backed up a few steps, then lunged forward and leaped, arms outstretched. His fingertips caught the open space where the panel had been pushed ajar. Hanging there with one hand, he shoved at the panel with the other. It hardly moved.

"No leverage," Doug gasped.

"Stand on my shoulders," said Brudnoy, ducking under Doug's flailing feet. "Then you can use both hands."

"You knew this would happen all along, didn't you?" Doug asked, as Brudnoy straightened up under him. He pushed the panel aside; it screeched like a rusty hinge.

"Simple physics," Brudnoy said.

Doug hauled himself up into the vent 'Thanks," he said, looking down at the Russian.

"There you are!" It was Zimmerman, hurrying along the tunnel. He reminded Doug of a big sea lion waddling across a beach.

"You should be in your quarters," Doug called down to him.

"So? I will be safer there?"

Brudnoy turned slightly to hide the smile that the professor's sarcasm triggered.

"We can't have people just wandering around the base," Doug said.

"I am not wandering. I came looking for you."

"Oh? Why?"

"To warn you."

Brudnoy's smile vanished. "Of what?"

Waggling a stumpy finger up toward Doug, Zimmerman said, "You think you are superman, maybe, because you have the nanomachines in you?"

Doug blinked down at the professor. "I hadn't even thought about that."

"Good. Forget about them. They will not make you into a hero. They cannot protect you from all harm."

"I didn't think they could," Doug said.

"They are medical, metabolic," Zimmerman went on. "They can heal injuries quickly. But that is all they can do for you."

"Okay," said Doug.

"Do not think you can perform superhuman feats. You cannot"

"Okay," Doug repeated, feeling slightly exasperated "Thanks for the warning. I've got to get going now."

"Yah. I know." Zimmerman stood there fidgeting for a moment, men said in the softest voice Doug had ever heard out of him, "Good luck, my boy."

Grinning, Doug replied, "Thanks."

Brudnoy handed him the power drill they had brought with them. Doug grasped it, men started to worm around for his trek down the vent "Turn on the transponder," Brudnoy reminded.

"Yeah, right." Doug reached for the little black box clipped to his chest pocket and pressed its stud. Now they could track his progress back at the control center. If I get killed, he thought sardonically, at least they'll know where to find the body.

"One more thing," Brudnoy called.

"What?" Doug asked, getting irritated at the delay.

"I want you to remember something your father often said. Every time he had a difficult job to do, he said it"

"My father?" Doug asked, more gently.

"If it is to be, it's up to me," Brudnoy said. "That was your father's motto."

"If it is to be, it's up to me," Doug repeated.

"Yes," said Brudnoy.

"Thanks, Lev. That's good to know."

"Good luck."

"Right."

Brudnoy and Zimmerman watched the young man disappear into the darkness of the overhead vent.

"Come on," said Brudnoy to the professor. "Time for us old men to go wait with the women."

Zimmerman shook his head, glanced up at the ceiling, then let Brudnoy lead him back toward the control center.

Doug tucked the hand drill into the thigh pocket of his coveralls and undipped the penlight from his chest pocket. The pencil beam seemed feeble as he swung it back and forth. The vent was barely wider than his shoulders, and caked with dust. Should've brought a breathing mask, he said to himself. At least there won't be any rats or bugs. Shouldn't be. All the inbound cargoes are checked Earthside and on arrival here. There won't be anything in this vent to surprise me. Couldn't be.

But he knew he was trying to convince himself of something he was really unsure of.

Joanna almost threw herself at Brudnoy when he and Zimmerman came back into the control center.

"He's in the vent?" she asked, her voice high with tension.

Brudnoy said as soothingly as he knew how to, "He's on his way. He'll be at the EVC in half an hour, at most"

Anson muttered, tight-lipped, "They can do a lotta damage in half an hour, I betcha."

Brudnoy shrugged. "As long as they don't damage the recycling equipment too badly..."

"Good thing they don't have any explosives in there," Anson said, turning back to the wall screen.

"It's a question of time now," Brudnoy said to Joanna. "Can Doug get there soon enough to stop them from doing too much damage."

Joanna fought to keep back her tears. Doug was going to have to fight Greg. At best, only one of her sons would come out of this alive, she knew.

"We're picking up his transponder signal," called one of the technicians from his monitoring station.

"Put it on the big screen," Anson commanded.