'It was a cobalt alloy,' was the answer.

'Make that information a secret ... to S. P. officers only,' Pete said. 'Use your radiation probe on the lava we dump. I think we've found one of the old, pre-World War III, American missile sites. Possibly the main one that was built just before the blowup. I don't know who Love and Tolliver are working for, and I don't know why the secrecy, but we'll keep on acting as if this were only a rescue operation, and see what happens. Keep an eye on Tolliver. If he does anything too unusual, or potentially dangerous to me, let me know by clicking twice on the vacuum suit radio,' Pete said.

'Tolliver seems normal, just inexperienced.'

'That's what makes me wonder about him,' Pete said. 'I can't think of any reason Love would send a new recruit out to me, especially under the circ.u.mstances.'

'Warn the patrol at the next vent what's coming! Shoot that smoke bomb off the handle,' Larry said to one dispatcher, then turned to the other. 'Is he moving yet?'

'No.'

'Get that patrol out of the smoke back to 1 North.'

There was a short pause, then a dispatcher announced, 'He's advancing south.'

'Bring some containers down I to 1 North. We'll need them.'

Now Larry watched as the smoke bomb approached the next vent. The handle it was attached to was shot off and it veered off to one side, where it hit a pa.s.senger stop. The smoke bomb on the handle just behind it wasn't expected. One of the men snapped off a shot at it and missed. Again a patrol was engulfed.

'Warn the patrols! Several bombs on the handles!'

The dispatcher barely had time to pa.s.s the word. The patrol at 1 North shot down the second smoke bomb but missed the third. By the time they could see it, it was too late to shoot at it.

'Tell everyone, if they're in smoke, get out of it !'

The patrol at the next vent missed entirely. The patrol at J and Zero shot down the third smoke bomb. It went a little past the intersection before stopping. There was no smoke bomb behind it.

One of the men in the patrol had the presence of mind to get to the bomb, scoop it up with his armored hand and fling it back down the tunnel it came from. The intersection started clearing of smoke almost immediately.

'How soon before that first patrol comes out of the smoke?' Larry asked.'

'What do you mean?'

'I told you to get them out of the smoke. When do we see them?'

'We won't,' the dispatcher said. 'I sent them up an exit shaft.'

For a moment Larry was surprised. He shook his head and sighed. 'I've been thinking in one dimension. Good man! Tell the patrol at J and Zero to knock down and throw back anything that comes out of that smoke. And get some reserves in there to back them up. And my personal compliments to the man who threw the smoke bomb back. Good job!'

'Countdown on the intruder approaching J and Zero,' another dispatcher announced. 'Five, four, three, two, he's stopped, short of the intersection.'

'They located the hole in tunnel exit A2N36.'

'Have the computer calculate where an equivalent hole from the western Bergenholm to tunnel J would be,' Larry directed.

The dispatcher was puzzled. 'How do I do that?' he asked.

'Call Central Files and ask the computer what information it needs to solve the problem,' Larry answered, then turned to a free dispatcher. 'Advance the patrol at J and 2 North through the intersection into tunnel J. Have them put the smoke bombs in containers as they advance.'

'They're already at the second vent. The smoke beyond that point is too dense for them to find the bomb.'

'Ah ...' Larry thought back. That was where the first bomb was shot off a handle. 'That bomb is about 30 ...' He mentally reviewed what he had seen. The flight of the bomb could have lasted anywhere from a half to two or three seconds. He hadn't specifically timed it. He had been more interested in the bomb behind it. Three seconds. ' ... to 300 feet up the tunnel.' The second bomb had been shot off a handle at the intersection of J and 1 North, so it should be on the other side of the intersection, Larry reasoned. 'There should be clean air behind this one. Have the patrol check ... No wait, you can check J and 1 North, with the camera at the west end of 1 North. Quiz the monitors.'

'The intruder is backing up, north in J, again.'

Larry returned to the face on the visiphone that replaced Rog Philips. 'Who are you?'

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'Robert Niven.'

'OK, Niven. How much longer till the handles are stopped?'

'I don't know,' Niven said. 'I'll find out.' He turned away from the phone.

Everyone seemed busy except Dr. Kelvin. Larry noted the fact but couldn't think of anything for him to do, so they both waited and watched for awhile.

'He's stopped again, short of J and 1 North,' the dispatcher monitoring the spy-ray team announced.

'Someone just dumped a smoke bomb in that intersection,' another dispatcher reported.

'He probably just kicked the old one out where it'll spread smoke in the most directions. Get that patrol at the second vent in fast to get that next bomb,' Larry said.

'The intruder is moving south in J,' the dispatcher continued.

'Get a patrol in from I and 1 North to can the smoke bomb in the intersection of J and 1 North,'

Larry instructed an available dispatcher. Then he asked the dispatcher struggling with the Central File computer, 'Have you got his destination yet?'

'The Central File computer says there's no exit that fits.'

'Dr. Kelvin. Help this man. His problem is vital,' Larry said.

The spy-ray team dispatcher started the countdown for when the intruder would arrive at J and Zero.

The patrols stood, armed and ready. Waiting for whatever might come out of the smoke-shrouded tunnel in front of them.

Again the intruder stopped short of the edge of the cloud. And again those waiting were surprised.

This time instead of a smoke bomb, a light grenade had been tied to a handle. The television camera darkened to protect itself from burning out. The helmet visors of the men in the patrol blackened in the actinic light, as their armor automatically protected their eyes.

The blinding light came up to the patrol, and stopped! The handles had been turned off.

Larry swore. 'Knock down that grenade and throw it back into the smoke,' he said.

The intruder had already moved into the intersection under cover of the light grenade and had set off another smoke bomb. No one could see him behind the light grenade, nor was anyone aware of the smoke until first the light grenade and then the patrol began fading into the spreading darkness.

'Get that patrol out of there,' Larry commanded but this time he had the feeling that he was in serious trouble. It wasn't aided by Dr. Kelvin's announcement that they had the intruder's destination.

'He's headed for a point about 20.5 feet up exit shaft JOS10. The projected hole will pa.s.s into it in about three minutes and take about 50 minutes to pa.s.s through it,' he said.

'What was the problem?'

'Remembering to update the projected hole to its present time orientation. Luna rotates, you know.'

Larry turned to a dispatcher. 'Is JOSl0 in the smoke?'

'Yes. It is now.'

'Can you get a patrol to a doorway in that shaft without going through the travel tunnels?'

'It'll take awhile to go around through the regular pa.s.sages to it. They're sort of sketchy back there.'

'Get them going then,' Larry said.

A few moments later a dispatcher switched his earphone to a loudspeaker and Larry heard the choking sound of a man dying in agony.

Ed Baker was a young, idealistic, dedicated, optimistic, polite and energetic security officer. He embodied all of those qualities the public feels a security officer should have. He was also new to the job, which is why he still retained some of them.

He was in the patrol facing the light grenade. Momentarily blinded, he had tried to shoot it down, to throw it back as he had the smoke bomb. When it began to fade, he supposed that it was burning out. Then he realized that everything was fading into a h.o.m.ogenous gray. The dispatcher told his patrol to withdraw, preferably up the nearest exit shaft. Baker hesitated. For him the nearest shaft upward was toward the light grenade. The other men seemed to interpret the order by pulling back to the next shaft. Baker felt that someone should go up the shaft near the grenade, just in case it was important. He moved over until he was underneath the shaft and then hesitated on the pa.s.senger stop. The light grenade was drifting near and it seemed that the smoke was thinner in its vicinity. He could see, he rationalized, and therefore he wasn't really in the smoke. If the grenade went out, he was in position to immediately go upward and out of the smoke. He waited on the pa.s.senger stop, trying to see the far side of the travel tunnel. The grenade slowly drifted nearer.

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When the intruder attacked, Baker realized how poorly thought out his idea had been. The smoke was far thicker than it seemed. The intruder had seen him in his exposed position on the pa.s.senger stop and had gone past him without being seen. Then he had come up from the rear, put his arm around Baker's neck and jammed his gun against the armor's shield at the neck joint. Baker struggled. He had time to give one yell for help, which turned into a cry of agony as the beam cut through his armor ... and he died The alien lost no time in stripping the armor from the dead security officer. Only a slight adjustment of the clasps and clamps was necessary for it to fit Before putting on the last gauntlet, he looked at his wrist.w.a.tch. He was on schedule. The couple of minutes required to get to his destination would make it time to start. He hoped his would be the last Bergenholm. The lightning-like response of security to his sabotage had not been antic.i.p.ated. He was not sure he could make it to the third Bergenholm, even protected by his stolen armor. He hurried off through the smoke toward his next destination, the bags flapping outside his armor like strange wings.

Rog Philips stood a few feet away from the video camera overlooking the western Bergenholm vault, a large, gray, concrete block behind a green shield in the center of an even larger chamber. He had called McQueen on a pocket communicator to report his arrival. 'What's happening?' he asked.

'The intruder got another of our men,' Larry answered. 'He may attack that vault any moment now.'

'I'll go over to the vault door and be ready with the first key when Hanovich arrives. Is the generator in the south vault off yet?'

'Yes,' Larry answered. 'I've already evacuated the tunnels. The generator in your vault is the only one on. Get it, turn it off, wait 10 minutes and then turn it back on.'

'Right,' Rog agreed, and walked over to the door of the vault. He waited, key in hand for Hanovich, resisting the temptation to put the key in the outer door of the vault for fear of starting to open it prior to Hanovich's arrival with the second key.

Hanovich appeared in the entry way to the chamber and started across the intervening s.p.a.ce. He was breathing hard from having run so far. Opposite the entry, from behind the vault, there came an explosion, the pure noise of matter impacting with meteoric effusion. The intruder had begun cutting through the wall into the chamber.

Hanovich started to run. It was the sloppy run of a man already near the limit of his endurance, trying for a little more.' Now a blast of dust and pieces of rock came from behind the vault, narrowly missing Hanovich. The intruder was through the chamber wall. There was a pause: the lull before the storm.

Hanovich was almost to the door of the vault when a deafening thunderclap made both men reel. It was followed by an intense wave of heat. The first tube of sand had come through the hole, expending most of its energy enlarging it.

Rog Philips was up first. He had the key in the door, turned it and was pulling on the first vault door when Hanovich got to him to help. They went inside. Hanovich fumbled for a moment in his pocket for the second key. He had not trusted himself to carry it in his hand for fear of dropping it. He had turned the key in the door when the second tube of sand hit the vault. The floor bounded under their feet, knocking them to their knees. Hanovich got up and leaned on the door. It opened and he went inside. Philips was on his heels. Inside Philips led the way, heading directly to the control panel for the artificial gravity generator. Hanovich trailed him, not being familiar with the inside of the vault.

The third container of sand struck the vault and the floor lurched underfoot in waves as though the vault were afloat instead of on solid rock. The motion of the floor caught Rog Philips off balance in the midst of a stride. He pitched forward, hitting his head against a switch handle protruding from a panel. He went down unconscious and bleeding from the blow.

Hanovich bent over Philips. He shouted his name and shook him. Phillips lay limp in his hands. For a moment Hanovich felt the full emotions of panic. He froze. He was alone. The full weight of responsibility for saving Copernicus was on his shoulders, and he didn't know how to do it. He shook Philips again and shouted his name. Nothing. Philips might have been dead for all the response he gave. Hanovich shuddered. The panic died away into an unreality of coldness. He was alone. There would be no help coming from Philips or any other source. Whatever he could do, he would have to do himself. Now. Where was the power switch to the artificial gravity?

Hanovich stood up. He looked for the first time at the control panel Philips had hit. Looked and saw. Three beautiful words looked back at him, all in capitals: ARTIFICIAL GRAVITY GENERATOR. The power switch was just underneath the sign.

As if in a dream Hanovich reached out and grabbed the handle of the switch. At the same moment the fourth tube struck. He held on as the floor again heaved under his feet. The alarm on the vault shield started screeching. The outer shield generator was overloaded, burning out.

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Hanovich pulled down on the switch and with a soul-satisfying 'clunk' it opened. The control panel lit up with red lights like a Christmas tree. He stepped back to see if there might be something else he could do. He couldn't see anything else, so he stood there a moment waiting for the impact of the next tube. Then he tried to help Rog Philips.

Throwing the switch on the artificial gravity generator marked the end of the crisis.

In the travel tunnel the alien, clamped to the wall with magnets, couldn't breath. The smoke and air around him was visibly falling to the bottom of the tunnel, drawn there by the force of natural gravity. Even in his lungs only the lower portion of his alveoli had contact with air. He tore the magnets loose and tried to go up the exit tube. Too late. Air pouring through the doorway had produced a local pressure drop. The falling pressure was detected and automatic equipment closed the door. He clamped his magnets to the wall and tried to cut through the door with his torch. He failed; and in failing first fell unconscious, and then died, hanging by the magnetic belt in front of the exit door.

The security patrol sent to exit JOSl0 called in to report the exit door closed. They were told to wait.

The crew in the south vault reported their Bergenholm operating.

Hanovich found Philip's pocket communicator and answered its buzzing. He requested an ambulance and gave a quick report of what had happened.

Finally the a.s.sistant Director of Maintenance, Robert Niven, reported with a wry smile that he had just been informed that the handles in tunnel J had been turned off. For a moment no one realized what he was talking about. When they did, the dispatchers in the control center greeted this announcement with laughter and a few cheers.

There would be hours of cleanup before the travel tunnels could again be open to the public, or anyone except authorized personnel. The entrances and exits would remain locked until they were individually opened. But this crisis was past and Copernicus still existed.

CHAPTER TWELVE.

MISSION: SOLARIAN PATROL DESTRUCT.

The security team interviewing members of the work party who had helped open the entrance had not located the second alien. They were still hunting for a prospector who had entered Copernicus shortly after the alien disappeared, suspecting that perhaps he had come in with him.

Larry made certain that the Customs station now set up at the west entrance was alert for the second alien. Then he considered his next move. His only remaining lead was the group in the Consular Suite. He needed more information about them and that facility.

He left the control center for the surveillance room. His black-and-silver s.p.a.ce uniform, and the fact that he was already inside Security's restricted area, permitted his unimpeded pa.s.sage. He rang the door alarm and was met by the man who had previously answered his question about the actions of the inhabitants in the suite.