'Well, this is a miniature version of the big digger. It drags a slick plastic tube behind it. On earth they use teflon. Here the rock is below -100 F so we have to use Slipon. Teflon begins to cold flow. It's used to supply air to trapped miners. Goes through rock like a bat out of you know where,' Copernicus Control said.

'But Harv is buried in loose rock,' said Pete.

'It has a special spiked head for that,' Copernicus Control explained. 'It'll dig all the faster.'

'OK, any other gadgets I haven't heard of ?' asked Pete.

'Nope, call me when you get to Mayer A,' Copernicus Control said.

'How come you don't use a full-sized digging machine to get the entrances clear?' Pete asked.

'It would take too long to wrestle one up to an entrance,' came the answer. 'They are all down south clearing out a new lab.'

'Right. Thanks. Bye,' Pete said and signed off.

'How long is the period between observing satellites?' Pete asked the moon creeper a little while later.

'They overlap,' the moon creeper said.

'How come there was a delay yesterday in talking to Harv?' asked Pete.

'The slope of Mayer A's walls is such that it takes about eight minutes after the first satellite goes down until the next satellite rises from the horizon to see down inside it,' was the answer.

'Can we manage to be pa.s.sing Harvey's carrier while neither satellite is watching?' Pete asked.

The creeper was silent for a moment while calculating arrival times and satellite transitions.

'Yes,' was the answer. 'if we speed up another tenth of a mile per hour, there are no slides on the trail near the crater, and if we have no trouble getting over the rim of the crater.'

'OK, arrange it so we are just pa.s.sing Harv's carrier as we go out of sight of the satellite. I want to check inside without having anyone looking over my shoulder while I'm doing it,' Pete said. 'After we check it, we hustle over to the slide and make tut-tut noises with Harv until the digging equipment arrives.'

Traversing into a crater is a particularly ticklish operation. The inside edge of a crater is usually smooth, circular, and steep. The outside is usually somewhat rough and not so steep. if the height from the outside to the rim of a crater is considered one unit of distance, the depth from the rim to the bottom is about three units, and the diameter is about twelve units. The walls are over 45 in slope near the rim. Pete's moon creeper climbed the outer wall, started around the rim picking up speed, and then dropped inside. It spiraled down the steep face until it could stop without sliding.

'We are right on schedule,' the moon creeper reported to Pete. Pete was suited up ready to get Out. The moon creeper reported the satellite out of sight and stopped at Harvey's carrier almost simultaneously. Pete got out and jumped to the carrier. He unlatched the top, and activated the jacks. The top lifted and Pete spent a minute looking at the insides. After the initial surprise, he examined it with extreme care. He made certain there were no mechanisms attached to the lid which might leave evidence that it had been opened. There were none. He went back to the moon creeper, got a spare control unit, and exchanged it for Harvey's. He noted the information on the nameplate of the 'carrier,' and then closed the lid.

Pete was back inside the moon creeper with minutes to spare. The cabin was re-pressurized, and as Pete stripped off the vacuum suit he said, 'Get moving at high speed toward the slide. We've got some apparent time to pick up. As soon as I get this suit off, contact Harv. Can you handle a SP/RFU-16?'.

'Yes, that's part of our back-ground instructions,' answered the moon creeper.

'Your auxiliary channel two is connected to one. That so-called carrier out there is a Solarian Patrol remote fighting unit. Whatever Harv was doing, he was really loaded for bear! That 'carrier' could have been square in the path of the slide, and not a rock touch it!' Pete said.

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'Suit's off and stashed.'

'Here is Harvey,' the moon creeper announced.

'Hi, Harv. Quite a rockpile you've got there!'

'Hm-m-m! Stupid huh!' answered Harvey.

'Come off it, Harv. You know we didn't mean it when we kidded you. If you were so stupid, you wouldn't have survived to become an old-timer,' Pete answered.

'Go on...'

'What do you mean?'

'It's nice to hear something complimentary about yourself, even if it is left-handed,' answered Harv.

'So you're kind, brave, obedient, reverent, thoughtful, clean, honest, and true, and everyone byes you all to pieces. OK?' Pete said.

'Nuts!'

'Any idea where in the slide you are?' asked Pete.

'No.'

'Creeper, plot his radio direction. We'll have you pinpointed in a couple of minutes,' Pete said.

The creeper ran along the edge of the slide for several minutes while Pete and Harv continued talking.

'Indications are that you are about as near to the center of the slide as you can get. You're about three hundred feet back from the nearest edge, and maybe about forty-five feet down, give or take a couple of feet in any direction. When the equipment gets here I'll be able to locate you closer with the portable spy-ray. Is the satellite up yet?' Pete said.

'Yes,' answered the creeper.

'Show them our view of the slide, and tell them to hurry it up,' Pete said.

'Copernicus Control wants to talk to you,' said the creeper.

'OK. Put them on,' Pete said.

'We were listening to you when you placed Harv's location in the slide. It looks like you just have to cut through to him and drag him out,' said Copernicus Control.

'Not quite. We lucked out in that he isn't at the bottom of the slide, but it still isn't quite that simple. I'll talk technique when I have some equipment to work with. Is the equipment on its way yet?' Pete asked.

'No, you've got another two hours before the entrance is cleared,' answered Copernicus Control.

'Then there's not much I can do except to survey the slide on foot, and try to figure out how we're going in after Harv,' Pete said.

'We'll call back when the entrance is open,' Copernicus Control said and signed off.

During the following hours Pete explored the slide and the area where the slide started. He saw nothing except a jumble of rock. Copernicus Control called to announce that the equipment was on its way. Pete estimated cutting times, equipment placement, talked to Harv and slept.

It took the work party a day of steady traveling to get to the blocked, western entrance. It was located within a thousand yards of the slot being cut around Copernicus. The work party had bypa.s.sed the northmost entrance for this one nearer the city. Tractor beam projectors on trailers were anch.o.r.ed in place. In a few minutes they were being used to move the debris out of the entrance. As soon as access was obtained, men with cutters were removing the battered metal of the airlock. Both the inner and outer doors had been damaged beyond any possible repairs. The impact of the secondary meteorites had been so violent that the surface sheets of metal were bent outward in the direction the rocks had come from, typical of hypersonic impact. Rocks were removed from inside the airlock. Then the inner doors and damaged facilities behind the airlock were removed.

The airless tunnel was now open to the slot, where more debris and a cave-in was removed. Ahead was an airtight door which had been modified into a second airlock on the other side of the slot.

This second airlock would now become the main airlock of this tunnel. There had been no real danger to Copernicus. Airtight doors were located about every thousand feet in the tunnel. They closed automatically at any drop of pressure.

Waiting in the tunnel beyond the damage was a moon-car, a wheeled vehicle built to step over obstacles. It looked like a tincan with two pairs of tandem wheels supporting each side. Each pair of wheels, one behind the other, was connected to a short beam. The beam was pivoted to the side of the vehicle so the entire wheel unit could rotate through a complete circle. At the moment each wheel unit was partially rotated so only four wheels of the eight were touching the ground, giving the impression of the mooncar being up on tiptoe.

Two men left the work crew and climbed the short ladder to the airlock in the rear of the vehicle.

A few minutes later one of the men returned to the work crew. Inside the other had disconnected 3940

the electronic brain controlling communications and had the driver at gun point.

As soon as the way was clear, the mooncar with its trailers moved out and started on the Northwest Trail, out toward the crater Mayer. About 40 miles along the trail the mooncar stopped to 'check the trailers'. No one noticed the body dumped into a small crater and covered with rocks. The new driver continued on his way.

'What happened to your buddy?' the foreman asked the man who had remained behind.

'Oh, he's around somewhere,' the man said, shrugged, and nodded toward the cleared entrance to Copernicus. 'Do you mind if I go back in?'

'Sure. We're about done here. A transporter will be going into Copernicus in about 15 minutes. The next crew can take care of the other entrances.'

'The single, most critical point of attack in Copernicus is the travel tunnel system,' Rog Philips said. He and Larry stood at the entrance to a metal vault watching a group of men work on an enormous Bergenholm inertia-neutralizing generator. 'It represents a danger to the city even under normal circ.u.mstances. The travel tunnels lie underneath the whole city. They're surrounded by 100,000 cubic yards of plastic and metal, the tunnel liner, which is held inertialess. You can imagine what would happen if suddenly that material's original inertia were restored and it took off upward at 30 miles per second. The travel tunnels would slice through Copernicus like a razor- sharp cutter slicing a potato into french fries.'

'We've taken extensive precautions to minimize the danger. There are three Bergenholms producing the state of inertialessness. Each is capable of maintaining the whole system alone. Each uses city power but also has its own auxiliary power source. Each is in a different location, widely separated from the others. Each is installed in a double locked time vault, one of the keys to which is normally only in the possession of the Directors of Maintenance, Security, and the Mayor.

Each vault faces a different direction, away from the city. Griffin's men have gained entry to each of the vaults for "routine maintenance". I've concentrated the efforts of my repair crew on this unit. It has been completely checked out. Mike,' Rog called the foreman of the crew over.

'Mike, will you tell Lt. McQueen what you found.'

'Yes,' Mike said. 'We found an explosive bolt installed in a critical a.s.sembly of the Bergenholm, and explosive mixed with the fuel of the auxiliary power supply. The explosive bolt could be exploded at any time by sending the proper signal over the power lines. The auxiliary power supply would have been destroyed within a few minutes any time it was used. We're ready to close the vault and start on the next one.'

'Go ahead,' Rog Philips said.

The inner vault door was closed. The first key locking it was removed. A minute later the green radiance of a wall shield covered the door. Then the outer doors were closed and the second key locking them removed.

'When the outer door is opened, the wall shield goes down for one minute,' Rog Philips explained.

'After that it goes down for one minute each hour. The wall shield is capable of withstanding any known portable weapon and we've changed locks so there's no chance of Griffin or any of his people getting in.

Larry looked around the large room completely surrounding the vault so it could be inspected from all sides except the bottom. He noticed television cameras on the walls but didn't comment on them; instead he asked, 'Sounds like you should check the power system for some way it could be disrupted?'

'Yes,' Rog answered, 'but where? The main generators? The distribution system? The sub-stations?

It's a big system. We've isolated the main generators and I've men checking the distribution system but nothing's turned up yet. We've checked, and replaced the fuel supplies of all the standby power systems as soon as we found this one contaminated.'

Larry's belt buzzed. 'Yes?' he answered.

'This is Col. Hanovich. Would you come to Security? I think we've found some more aliens.'

'I'll be right there,' Larry answered.

A tall, shapely blonde woman stood in front of a mirror putting on eye makeup. A mile away a 3- dimensional image of her stood in front of Lt. Larry McQueen doing the same thing.

The name of the door of the room he was in had said Surveillance. The woman was inside on a low stage in the center of the room, with projectors and consoles around it. Three security officers sat at the consoles operating the controls, watching and listening.

'The Customs Officer was suspicious so he put a tracer on the ambulance,' Hanovich said. He was standing a little behind Larry and to one side. 'We followed them to the hospital and then to the hotel. They spent the night in the Consular Suite.'

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The woman stepped back and turned her head from side to side, surveying her work critically. She started making slight changes.

'Who is she?' Larry asked.

'She's registered as Jan Vierliter, Tellus.'

Almost as if she had heard, the woman hesitated and smiled.

'The others?'

'Heinrich Geis of Procyon. Bernard Hermond, his bodyguard. And Dr. Karl Kalb, his personal physician.'

'What made the Customs Officer suspicious?'

'They were carrying these,' Hanovich said, holding out two small objects that looked like standard power cord plugs. 'We traded theirs for some dummy duplicates. The lab says that they are power line oscillators. They put a coded signal on the power line when connected to it.'

Larry looked at one for a moment. 'One of Rog Philips' men just told me about some explosive bolts installed on a travel tunnel Bergenholm. These might be the detonating device for them,' he commented. 'Anything else?'

'Nothing until just before I called you,' Hanovich said. 'I got a reply from Procyon. They have never heard of any of these people, and the ship that landed them used a fict.i.tious registry.'

'What have they done since they got here?'

'Nothing,' Hanovich answered in a discouraged tone. 'Nothing except play cards, watch television and make small talk. They landed on emergency priority, came dashing in and then sat for a day doing nothing. Why?'

'Are you positive that that's all they've been doing? How can you tell?'

There was a long pause. Hanovich's face broadened out into a smile. Larry had time to realize that he had just put his foot into it. He could almost hear Hanovich say 'Gee, I thought you'd never ask' from his expression as he waited for the lecture on how clever Security was in general, and Hanovich in particular, to come. It did.

'We built the Consular Suite over a hundred years ago as a special surveillance system. Occupants of the suite can be watched as closely as is necessary, and can be confined, if desired. The walls of the suite are 10-foot-thick reinforced concrete backed by almost 100 feet of solid rock. The front door is the only entrance and the corridor to it is kept unsealed remotely. Otherwise it would be an even stronger barrier than the walls. The air, water, power and communications are isolated from the rest of Copernicus. We can watch and listen to everything that happens there with complete safety, regardless of what the occupants of the suite do or where in the suite they go.'