"Chee?" he asked anxiously.
"They've gone away," growled Calhoun. "They probably left in ground-cars. There's not one in sight."
There wasn't. Calhoun could look out through the grid foundations and see long, sunlit and absolutely empty streets. He arrived at the spaceport building. There was—there had been—a green area about the base of the structure. There was not a living plant left. Leaves were wilted and limp. The remains had become almost a jelly of collapsed stems and blossoms of dark olive-green. The plants were dead; but not long enough to have dried up. They might have wilted two or three days before.
Calhoun went in the building. The spaceport log lay open on a desk. It recorded the arrival of freight to be shipped away—undoubtedly—on the Candida now uneasily in orbit somewhere aloft. There was no sign of disorder. It was exactly as if the people here had walked out to look at something interesting, and hadn't come back.
Calhoun trudged out of the spaceport and to the streets and buildings of the city proper. It was incredible! Doors were opened or unlocked. Merchandise in the shops lay on display, exactly as it had been spread out to interest customers. There was no sign of confusion anywhere. Even in a restaurant there were dishes and flatware on the tables. The food in the plates was stale, as if three days old, but it hadn't yet begun to spoil. The appearance of everything was as if people at their meals had simply, at some signal, gotten up and walked out without any panic or disturbance.
Calhoun made a wry face. He'd remembered something. Among the tales that had been carried from Earth to the other worlds of the galaxy there was a completely unimportant mystery story which people still sometimes tried to write an ending to. It was the story of an ancient sailing ship called the Marie Celeste, which was found drifting aimlessly in the middle of the ocean. There was food on the cabin table, and the galley stove was still warm. There was no sign of any trouble, or terror, or disturbance which might cause the ship to be abandoned. But there was not a living soul on board. Nobody had ever been able to contrive a believable explanation.
"Only," said Calhoun to Murgatroyd, "this is on a larger scale. The people of this city walked out about three days ago, and didn't come back. Maybe all the people on the planet did the same, since there's not a communicator in operation anywhere. To make the understatement of the century, Murgatroyd, I don't like this. I don't like it a bit!"
II
On the way back to the Med Ship, Calhoun stopped at another place where, on a grass-growing planet, there would have been green sward. There were Earth-type trees, and some native ones, and between them there should have been a lawn. The trees were thriving, but the ground-cover plants were collapsed and rotting.
Calhoun picked up a bit of the semi-slime and smelled it. It was faintly sour, astringent, the same smell he'd noticed when he opened the airlock door. He threw the stuff away and brushed off his hands. Something had killed the ground-cover plants which had the habit of killing Earth-type grass when planted here.
He listened. Everywhere that humans live, there are insects and birds and other tiny creatures which are essential parts of the ecological system to which the human race is adjusted. They have to be carried to and established upon every new world that mankind hopes to occupy. But there was no sound of such living creatures here.
It was probable that the bellowing roar of the Med Ship's emergency rockets was the only real noise the city had heard since its people went away.
The stillness bothered Murgatroyd. He said, "Chee!" in a subdued tone and stayed close to Calhoun. Calhoun shook his head. Then he said abruptly:
"Come along, Murgatroyd!"
He went back to the building housing the grid controls. He didn't look at the spaceport log this time. He went to the instruments recording the second function of a landing-grid. In addition to lifting up and letting down ships of space, a landing-grid drew down power from the ions of the upper atmosphere and broadcast it. It provided all the energy that humans on a world could need. It was solar power, in a way, absorbed and stored by a layer of ions miles high, which then could be drawn on and distributed by the grid. During his descent Calhoun had noted that broadcast power was still available. Now he looked at what the instruments said.
The needle on the dial showing power-drain moved slowly back and forth. It was a rhythmic movement, going from maximum to minimum power-use, and then back again. Approximately six million kilowatts was being taken out of the broadcast every two seconds for half of one second. Then the drain cut off for a second and a half, and went on again for half a second.
Frowning, Calhoun raised his eyes to a very fine color photograph on the wall above the power dials. It was a picture of the human-occupied part of Maya, taken four thousand miles out in space. It had been enlarged to four feet by six, and Maya City could be seen as an irregular group of squares and triangles measuring a little more than half an inch by three-quarters. The detail was perfect. It was possible to see perfectly straight, infinitely thin lines moving out from the city. They were multiple-lane highways, mathematically straight from one city to another, and then mathematically straight—though at a new angle—until the next. Calhoun stared thoughtfully at them.
"The people left the city in a hurry," he told Murgatroyd, "and there was little confusion, if any. So they knew in advance that they might have to go. They were ready for it. If they took anything, they had it ready packed in their cars. But they hadn't been sure they'd have to go because they were going about their businesses as usual. All the shops were open and people were eating in restaurants, and so on."
Murgatroyd said, "Chee!" as if in full agreement.
"Now," demanded Calhoun, "where did they go? The question's really where could they go! There were about eight hundred thousand people in this city. There'd be cars for everyone, of course, and two hundred thousand cars would take everybody. But that's a lot of ground-cars! Put 'em two hundred feet apart on a highway, and that's twenty-six cars to the mile on each lane. Run them at a hundred miles an hour on a twelve-lane road—using all lanes one way—and that's twenty-six hundred cars per lane per hour, and that's thirty-one thousand ... two highways make sixty-two ... three highways.... With two highways they could empty the city in under three hours, and with three highways close to two. Since there's no sign of panic, that's what they must have done. Must have worked it out in advance, too. Maybe they'd done it before it happened ... whatever it was that happened."
* * * * *
He searched the photograph which was so much more detailed than a map. There were mountains to the north of Maya City, but only one highway led north. There were more mountains to the west. One highway went into them, but not through. To the south there was sea, which curved around some three hundred miles from Maya City and put the human colony on Maya on a peninsula.
"They went east," said Calhoun presently. He traced lines with his finger. "Three highways go east; that's the only way they could go quickly. They hadn't been sure they'd have to go but they knew where to go when they did. So when they got their warning, they left. On three highways, to the east. And we'll follow them and ask what the hell they ran away from. Nothing's visible here!"
He went back to the Med Ship, Murgatroyd skipping with him.
As the airlock door closed behind them, he heard a click from the outside-microphone speakers. He listened. It was a doubled clicking, as of something turned on and almost at once turned off again. There was a two-second cycle, the same as that of the power drain. Something drawing six million kilowatts went on and immediately off again every two seconds. It made a sound in speakers linked to outside microphones, but it didn't make a noise in the air. The microphone clicks were induction; pick-up; like cross-talk on defective telephone cables.
Calhoun shrugged his shoulders almost up to his ears. He went to the communicator.
"Calling Candida—" he began, and the answer almost leaped down his throat.