The robots had not noticed them, for which all three were duly grateful. Ogden nudged the nearest to him – it happened to be Annamarie – and thrust out a bony finger. "Is that what the Mars-Tube looks like from inside?" he hissed piercingly.
As their eyes became acclimated to the gloom – they dared use no lights – the others made out the lines of a series of hoops stretching out into blackness on either side ahead of them. No lights anywhere along the chain of rings; no sound coming from it.
"Maybe it's a deserted switch line, one that was abandoned. That's the way the Tube ought to look, all right, only with cars going along it," Stanton muttered.
"Hush!" it was Annamarie. "Would that be a car coming –from the left, way down?"
Nothing was visible, but there was the faintest of sighing sounds. As though an elevator car, cut loose from its cable, were dropping down its shaft far off there in the distance. "It sounds like a car," Stanton conceded. "What do you think, Og – Hey ! Where's Josey?"
"He brushed me, going toward the Tube. Yes – there he is! See him? Bending over between those hoops!"
"We've got to get him out of there! Josey! " Stanton cried, forgetting about the robots in the light of this new danger. "Josey! Get out of the Tube! There's a train coming!"
The dimly visible figure of the Roentgenologist straightened and turned towards the others querulously. Then as the significance of that rapidly mounting hiss-s-s-s became clear to him, he leaped out of the tube, with a vast alacrity. A split second later the hiss had deepened to a high drone, and the bulk of a car shot past them, travelling eerily without visible support, clinging to and being pushed by the intangible fields of force that emanated from the metal hoops of the Tube.
Stanton reached Josey's form in a single bound. "What were you trying to do, imbecile?" he grated. "Make an early widow of your prospective fiancée?"
Josey shook off Stanton's grasp with dignity. "I was merely trying to establish that that string of hoops was the Mars-Tube, by seeing if the power-leads were connected with the rings. It – uh, it was the Tube; that much is proven," he ended somewhat lamely.
"Brilliant man!" Stanton started to snarl, but Annamarie's voice halted him. It was a very small voice.
"You loud-mouths have been very successful in attracting the attention of those animated pile-drivers," she whispered with the very faintest of breaths. "If you will keep your lips zipped for the next little while maybe the robot that's staring at us over the rim of the pit will think we're turbo-generators or something and go away. Maybe!"
Josey swivelled his head up and gasped. "It's there—it's coming down!" he cried. "Let's leave here!"
The three backed away toward the tube, slowly, watching the efforts of the machine-thing to descend the precipitous wall. It was having difficulties, and the three were beginning to feel a bit better, when —
Annamarie, turning her head to watch where she was going, saw and heard the cavalcade that was bearing down on them at the same time and screamed shrilly. "Good Lord - the cavalry!" she yelled. "Get out your guns!"
A string of a dozen huge, spider-shaped robots of a totally new design were charging down at them, running swiftly along the sides of the rings of the Tube, through the tunnel. They carried no weapons, but the three soon saw why—from the ugly snouts of the egg-shaped bodies of the creatures protruded a black cone. A blinding flash came from the cone of the first of the new arrivals; the aim was bad, for overhead a section of the cement roof flared ghastly white and commenced to drop.
Annamarie had her useless paralyzer out and firing before she realized its uselessness against metal beings with no nervous system to paralyze. She hurled it at the nearest of the new robots in a highly futile gesture of rage.
But the two men had their more potent weapons out and firing, and were taking a toll of the spider-like monstrosities. Three or four of them were down, partially blocking the path of the oncoming others; another was missing all its metal legs along one side of its body, and two of the remainder showed evidence of the accuracy of the Earthmen's fire.
But the odds were still extreme, and the built-in blasters of the robots were coming uncomfortably close.
Stanton saw that, and shifted his tactics. Holstering his heavy blaster, he grabbed Annamarie and shoved her into the Mars-Tube, crying to Josey to follow. Josey came slowly after them, turning to fire again and again at the robots, but with little effect. A quick look at the charge-dial on the butt of his heat-gun showed why; the power was almost exhausted.
He shouted as much to Stanton. "I figured that would be happening—now we run!" Stanton cried back, and the three sped along the Mars-Tube, leaping the hoops as they came to them.
"What a time for a hurdle race!" gasped Annamarie, bounding over the rings, which were raised about a foot from the ground. "You'd think we would have known better than to investigate things that're supposed to be private."
"Save your breath for running," panted Josey. "Are they following us in here?"
Stanton swivelled his head to look, and a startled cry escaped him. "They're following us—but look!"
The other two slowed, then stopped running altogether and stared in wonder. One of the robots had charged into the Mars-Tube—and had been levitated! He was swinging gently in the air, the long metal legs squirming fiercely, but not touching anything."
"How —?"
"They're metal!" Annamarie cried. "Don't you see—they're metal, and the hoops are charged. They must have some of the same metal as the Tube cars are made of in their construction—the force of the hoops acts on them, too!"
That seemed to be the explanation. "Then we're safe!" gasped Josey, staggering about, looking for a place to sit.
"Not by a long shot! Get moving again!" And Stanton set the example.
"You mean because they can still shoot at us?" Josey cried, following Stanton's dog-trot nonetheless. "But they can't aim the guns—they seem to be built in, only capable of shooting directly forward."
"Very true," gritted Stanton. "But have you forgotten that this subway is in use? According to my calculations, there should be another car along in about thirty seconds or less –and please notice, there isn't any by-path anymore. It stopped back a couple of hundred feet. If we get caught here by a car, we get mashed. So – unless you want to go back and sign an armistice with the robots? I thought not – so we better keep going. Fast!"
The three were lucky – very lucky. For just when it seemed certain that they would have to run on and on until the bullet-fast car overtook them, or go back and face the potent weapons of the guard robots, a narrow crevice appeared in the side of the tunnel-wall. The three bolted into it and slumped to the ground.
CRASH!
"What was that?" cried Annamarie.
"That," said Josey slowly, "was what happens to a robot when the fast express comes by. Just thank God it wasn't us."
Stanton poked his head gingerly into the Mars-Tube and stared down. "Say," he muttered wonderingly, "when we wreck something we do it good. We've ripped out a whole section of the hoops – by proxy, of course. When the car hit the robot they were both smashed to atoms, and the pieces knocked out half a dozen of the suspension rings. I would say, offhand, that this line has run its last train."
"Where do you suppose this crevice leads?" asked Annamarie, forgetting the damage that couldn't be undone.
"I don't know. The station ought to be around here somewhere – we were running toward it. Maybe this will lead us into the station if we follow it. If it doesn't, maybe we can drill a tunnel from here to the station with my blaster."
Drilling wasn't necessary. A few feet in, the scarcely passable crevice widened into a broad fissure, through which a faint light was visible. Exploration revealed that the faint light came from a wall-chart showing the positions and destinations of the trains. The chart was displaying the symbol of a Zeta train – the train that would never arrive.