Bigman felt dizzily helpless in the confusion. Hanging as closely as he could to the coattails of the restless Morriss, he found himself trotting from group to group, listening to breathless conversations which he did not always understand because of his ignorance about Venus.

Morriss had no opportunity to rest. Each new minute brought a new man, a new report, a new decision. It was only twenty minutes since Bigman had run off after Morriss, and already a dozen plans had been proposed and discarded.

One man, just returned from the threatened sector, was saying with pounding breath, "They've got the spy rays trained on him, and we can make him out. He's just sitting with the lever in his hand. We beamed his wife's voice in at him through the etherics, then through the public-address system, then through loudspeaker from outside. I don't think he hears her. At least he doesn't move."

Bigman bit his lip. What would Lucky do if he were here? The first thought that had occurred to Bigman was to get behind the man-Poppnoe, his name was-and shoot him down. But that was the first thought everyone had had, and it had been instantly discarded. The man at the lever had closed himself off, and the dome-control chambers were carefully designed to prevent any form of tampering. Each entrance was thoroughly wired, the alarms being internally powered. That precaution was now working in reverse-to Aphrodite's peril rather than its protection.

At the first clang, at the first signal gleam, Bigman was sure, the lever would be driven home and Venus's ocean would charge inward upon Aphrodite. It could not be risked while evacuation was incomplete.

Someone had suggested poison gas, but Morriss had shaken his head without explanations. Bigman thought he knew what the Venusian must be thinking. The man at the lever was not sick or mad or malevolent, but under mental control. That fact meant that there were two enemies. The man at the lever, considered by himself, might weaken from the gas past the point where he would be physically capable of pulling the lever, but before that the weakening would be reflected in his mind, and the- men in control would work their tool's arm muscles quickly enough.

"What are they waiting for, anyway?" growled Mor-. riss under his breath, while the perspiration rolled down his cheeks in streams. "If I could only train an atom cannon at the spot."

Bigman knew why that was impossible, too. An atom cannon trained to hit the man from the closest approach possible would require enough power to go through a quarter mile of architecture and would damage the dome enough to bring on the very danger they were trying to avoid.

He thought, Where is Lucky, anyway? Aloud he said, "If you can't get this fellow, what about the controls?"

"What do you mean?" said Morris.

"I mean, gimmick the lever. It takes power to open the lock, doesn't it? What if the power is cut?"

"Nice thought, Bigman. But each lock has its own emergency power generator on the spot."

"Can't it be closed off from anywhere?"

"How? He's closed off in there, with every cubic foot set off with alarms."

Bigman looked up and, in vision, seemed to see the mighty ocean that covered them. He said, "This is a closed-in city, like on Mars. We've got to pump air all over. Don't you do that, too?"

Morriss brought a handkerchief to his forehead and wiped it slowly. He stared at the little Martian. "The ventilating ducts?"

"Yes. There's got to be one to that place with the lock, doesn't there?"

"Of course."

"And isn't there someplace along the line where a wire can be wrenched loose or cut or something?"

"Wait a while. A microbomb shoved along the duct, instead of the poison gas we were talking about"

"That's not sure enough," said Bigman impatiently. "Send a man. You need big ducts for an underwater city, don't you? Won't they hold a man?"

"They're not as big as all that," said Morriss.

Bigman swallowed painfully. It cost him a great deal to make the next statement. "I'm not as big as all that, either. Maybe I'll fit."

And Morriss, staring down wide-eyed at the pint-size Martian, said, "Venus! You might. You might! Come with me!"

From the appearance of the streets of Aphrodite, it seemed as though not a man or woman or child in the city was sleeping. Just outside the transite partition and surrounding the "rescue headquarters" building, people choked every avenue and turned them into black masses of chattering humanity. Chains had been set up, and behind them policemen with stunguns paced restlessly.

Lucky, having emerged from rescue headquarters at what amounted to a dead run, was brought up sharply by those chains. A hundred impressions burst in on him. There was the brilliant sign in lucite curlicues, set high in Aphrodite's sky with no visible support. It turned slowly and said: aphrodite, beauty spot of venus, welcomes You.

Close by, a line of men were moving on in file. They were carrying odd objects-stuffed brief cases, jewel boxes, clothes slung over their arms. One by one, they were climbing into skimmers. It was obvious who and what they were: escapees from within the threatened zone, passing through the lock with whatever they could carry that seemed most important to them. The evacuation was obviously well under way. There were no women and children in the line.

Lucky shouted to a passing policeman, "Is there a skimmer I can use?"

The policeman looked up. "No, sir, all being used."

Lucky said impatiently, "Council business."

"Can't help it. Every skimmer in town is being used for those guys." His thumb jerked toward the moving file of men in the middle distance.

"It's important. I've got to get out of here."

"Then you'll have to walk," said the policeman.

Lucky gritted his teeth with vexation. There was no way of getting through the crowd on foot or on wheels. It had to be by air and it had to be now.

"Isn't there anything available I can use? Anything?" He was scarcely speaking to the policeman, more to his own impatient self, angry at having been so simply duped by the enemy.

But the policeman answered wryly, "Unless you want to use a hopper."

"A hopper? Where?" Lucky's eyes blazed.

"I was just joking," said the policeman.

"But I'm not. Where's the hopper?"

There were several in the basement of the building they had left. They were disassembled. Four men were impressed to help and the best-looking machine was assembled in the open. The nearest of the crowd watched curiously, and a few shouted Jocularly, "Jump it, hopper!"

It was the old cry of the hopper races. Five years ago it had been a fad that had swept the solar system: races over broken, barrier-strewn courses. While the craze lasted, Venus was most enthusiastic. Probably half the houses in Aphrodite had had hoppers in the basement.

Lucky checked the micropile. It was active. He started the motor arid set the gyroscope spinning. The hopper straightened immediately and stood stiffly upright on its single leg.

Hoppers are probably the most grotesque forms of transportation ever invented. They consist of a curved body, just large enough to hold a man at the controls. There was a four-bladed rotor above and a single metal leg, rubber-tipped, below. It looked like some giant wading bird gone to sleep with one leg folded under its body.

Lucky touched the leap knob and the hopper's leg retracted. Its body sank till it was scarcely seven feet from the ground while the leg moved up into the hollow tube that pierced the hopper just behind the control panel. The leg was released at the moment of maximum retraction with a loud click, and the hopper sprang thirty feet into the air.

The rotating blades above the hopper kept it hovering for long seconds at the top of its jump. For those seconds, Lucky could get a view of the people now immediately below him. The crowd extended outward for half a mile, and that meant several hops. Lucky's lips tightened. Precious minutes would vanish.

The hopper was coming down now, its long leg extended. The crowd beneath the descending hopper tried to scatter, but they didn't have to. Four jets of compressed air blew men aside just sufficiently, and the leg hurtled down harmlessly to the ground.

The foot hit concrete and retracted. For a flash Lucky could see the startled faces of the people about him, and then the hopper was moving up again.

Lucky had to admit the excitement of hopper racing. As a youngster, he'd participated in several. The expert "hop rider" could twist his curious mount in unbelievable patterns, finding leg room where none seemed to exist. Here, in the domed cities of Venus, the races must have been tame compared to the bone-breakers in the vast, open arenas of rocky, broken ground on Earth.

In four hops Lucky had cleared the crowd. He cut the motors, and in a series of small, dribbling jumps the hopper came to a halt. Lucky leaped out. Air travel might still be impossible, but now he could commandeer some form of groundcar. But more time would be lost.

Bigman panted and paused for a moment to get his breath. Things had happened quickly; he had been rushed along in a tide that was still whirling him onward.

Twenty minutes before, he had made his suggestion to Morriss. Now he was enclosed in a tube that tightened about his body and drenched him with darkness.

He inched along on his elbows again, working his way deeper. Momentarily he would stop to use the small flash whose pinpoint illumination showed him milky walls ahead, narrowing to nothing. In one sleeve, against his wrist, he held a hastily scrawled diagram.

Morriss had shaken his hand before Bigman had half-clambered, half-jumped, into the opening at one side of a pumping station. The rotors of the huge fan had been stilled, the air currents stopped.

Morriss had muttered, "I hope that doesn't set him off," and then he had shaken hands.

Bigman had grinned back after a fashion, and then he crawled his way into the darkness while the others left. No one felt it necessary to mention the obvious. Bigman was going to be on the wrong side of the transite barrier, the side from which the others were now retreating. If, at any time, the lever at the dome lock plunged down, the incoming water would crush the duct and the walls through which it ran as though they were all so much cardboard.

Bigman wondered, as he squirmed onward, whether he would hear a roar first, whether the surging water would make any hint of its presence known before striking him. He hoped not. He wanted not even a second of waiting. If the water came in, he wanted its work done quickly.

He felt the wall begin to curve. He stopped to consult his map, Ms small flash lighting the space about him with a cool gleam. It was the second curve shown in the map they had drawn for him, and now the duct would curve upward.

Bigman worked himself over to his side and bent around the curve to the damage of his temper and the bruising of his flesh.

"Sands of Mars!" he muttered. His thigh muscles ached as he forced his knees against either side of the duct to keep himself from slipping downward again. Inch by inch he clawed his way up the gentle slope.

Morriss had copied the map off the hieroglyphic charts held up before a visiphone transmitter in the Public Works Department of Aphrodite. He had followed the curving colored lines, asked for an interpretation of the markings and symbols.

Bigman reached one of the reinforcing struts that stretched diagonally across the duct. He almost welcomed it as something he could seize, close his hands about, use to take some of the pressure off his aching elbows and knees. He pressed his map back up his sleeve and held the strut with his left hand. His right hand turned his small flash end for end and placed the butt against one end of the strut.

The energy of the enclosed micropile, which ordinarily fed electricity through the small bulb of the flash and turned it into cold light, could also, at another setting of the control, set up a short-range force field through its opposite end. That force field would slice instantaneously through anything composed of mere matter that stood in its way. Bigman set that control and knew that one end of the strut now hung loose.

He switched hands. He worked his slicer to the other end of the strut. Another touch, and it was gone. The strut was loose in his fingers. Bigman worked it past his body, down to his feet, and let it go. It slid and clattered down the duct.

The water still held off. Bigman, panting and squirming, was distantly aware of that. He passed two more struts, another curve. Then the slope leveled off, and finally he reached a set of baffles plainly marked on the map. In all, the ground he had covered was probably less than two hundred yards, but how much time had it taken him?

And still the water held off.

The baffles, blades jutting alternately from either side of the duct to keep the air stream turbulent, were the last landmark. He sliced off each blade with a rapid sweep of his flash butt, and now he had to measure nine feet from the farthest blade. Again he used his flash. It was six inches long and he would have to lay it along the wall, end over end, eighteen times.

Twice it slipped, and twice he had to turn back to the slightly ragged marking of the last sheared baffle blade, scrambling backward and swearing "Sands of Mars!" in a whisper.

The third time the eighteenth measure landed truly. Bigman kept his finger on the spot. Morriss had said the desired place would be almost directly over his head. Bigman turned on his flash, ran his finger along the curved inner surface of the duct, twisted on to his back.

Using his slicer end and holding it, as nearly as he could judge in the dark, some quarter of an inch from actual contact (the force field must not slice in too far), he made a circle with it. Cleaved metal fell on him, and he pushed it to one side.

He turned his flash on the exposed wiring and studied it. Inches farther in would be the interior of a room not a hundred feet from where the man sat at the lock. Was he still sitting there? Obviously, he had not yet pulled the lever (what was he waiting for?) or Bigman would now be very water-logged, very dead. Had he been stopped then, somehow? Taken into custody, perhaps?

A wry grin forced itself onto Bigman's face as he thought that perhaps he was squirming through the interior of a metal worm for nothing.

He was following the wiring. Somewhere here should be a relay. Gently he pulled at the wires, first one, then another. One moved and a small, black, double cone came into view. Bigman sighed his relief. He gripped the flash with his teeth, freeing both hands.

Gingerly, very gingerly, he twisted the two halves of the cone in opposite directions. The magnoclasps yielded, and the two halves moved apart, exposing the contents. They consisted of a break relay: two gleaming contacts, one encased in its field selector and separated from the other by a nearly imperceptible gap. At an appropriate stimulus, such as the pulling of a small lever, the field selector set up the energies that would pull down the other contact, send energy streaming across the point of closure, and open a lock in the dome. It would all happen in a millionth of a second.

Bigman, sweating and half-expecting the final moment to come now, now, with his task a second from completion, fumbled in his vest pocket and withdrew a lump of insulating plastic. It was already soft from the warmth of his body. He kneaded it a moment and then brought it down delicately upon the point where the two contacts nearly met. He held it there while he counted three, then withdrew it.

The contacts might close now, but between them there would be a thin film of this plastic, and through it the flow of current could not pass.

The lever could be pulled now: the lock would not open.

Laughing, Bigman scrambled backward, made his way over the remnants of the baffle, passed the struts he had cut away, slid down the slopes...,

Bigman searched desperately for Lucky through the confusion that now flooded all the city. The man at the lever was in custody, the transite barrier had been lifted, and the population was flooding back (angry, for the most part, at the city administration for allowing the whole thing to happen) into the homes they had abandoned. To the crowds who had so ghoulishly waited for disaster, the removal of fear was the signal for a high holiday.

At the end Morriss appeared from nowhere and placed a hand on Bigman's sleeve. "Lucky's calling."

Bigman, startled, said, "Where from?"

"From my room in the Council offices. I've told him what you've done."

Bigman flushed with pleasure. Lucky would be proud! He said, "I want to talk to him."

But Lucky's face on the screen was grim. He said, "Congratulations, Bigman, I hear you were terrific."

"It was nothing," grinned Bigman. "But where've you been?"

Lucky said, "Is Dr. Morriss there? I don't see him."

Morriss squeezed his face into the viewer. "Here I am."

"You've captured the man at the lever, according to the news I hear."

"We did. We absolutely did, thanks to Bigman," said Morriss.

"Then let me make a guess. When you closed in on him, he did not try to pull the lever. He simply gave himself up."

"Yes," said Morriss, frowning. "But what makes you guess that?"

"Because the whole incident at the lock was a smoke screen. The real damage was slated to happen at this end. When I realized that, I left. I tried to come back here. I had to use a hopper to get through the crowd and a groundcar the rest of the way."

"And?" asked Morriss anxiously.

"And I was too late!" said Lucky.