drone through this sector. Each of the other drones was being monitored both by computer and by human observer, while Boardman and Hosteen were at the master terminal watching the progress of the entire operation all at once.
“Send them in,” Boardman said.
Hosteen gave the command, and the drones rolled forward through the city’s gates. Looking now through the eyes of the squat mobile probe, Rawlins got his first view of what lay in Zone H of the maze. He saw a scalloped wall of what looked like puckered blue porcelain undulating away to the left, and a barrier of metallic threads dangling from a thick stone slab to the other side. The drone skirted the threads, which tinkled and quivered in delicate response to the disturbance of the thin air; it moved to the base of the porcelain wall, and followed it at an inward-sloping angle for perhaps twenty meters. There the wall curved abruptly back on itself, forming a sort of chamber open at the top. The last time anyone had entered the maze this way—on the fourth expedition—two men had passed that open chamber; one had remained outside and was destroyed, the other had gone inside and was spared. The drone entered the chamber. A moment later a beam of pure red light lanced from the center of a mosaic decoration on the wall and swept over the area immediately outside the chamber.
Boardman’s voice came to Rawlins through the speaker taped to his ear. “We lost four of the probes the moment they went through their gates. That’s exactly as expected. How’s yours doing?”
“Following the plan,” said Rawlins. “So far, it’s okay.”
“You ought to lose it within six minutes of entry. What’s your elapsed time now?”
“Two minutes fifteen.”
The drone was out of the chamber now and shuttling quickly through the place where the light-beam had flashed. Rawlins keyed in olfactory and got the smell of scorched air, lots of ozone. The path divided ahead. To one side was a single-span bridge of stone, arching over what looked like a pit of flame; to the other was a jumbled pile of cyclopean blocks resting precariously edge to edge. The bridge seemed far more inviting, but the drone immediately turned away from it and began to pick its way over the jumbled blocks. Rawlins asked it why, and it relayed the information that the “bridge” wasn’t there at all; it was a projection beamed from scanners mounted beneath the facing piers. Requesting a simulation of an approach anyway, Rawlins got a picture of the probe walking out onto the pier and stepping unsuspectingly through the solid-looking bridge to lose its balance; and as the simulated probe struggled to regain its equilibrium, the pier tipped forward and shucked it into the fiery pit. Cute, Rawlins thought, and shuddered.
Meanwhile the real probe had clambered over the blocks and was coming down the other side, unharmed. Three minutes and eight seconds had gone by. A stretch of straight road here turned out to be as safe as it looked. It was flanked on both sides by windowless towers a hundred meters high, made of some iridescent mineral, sleek and oily-surfaced, that flashed shimmering moire patterns as the drone hurried along. At the beginning of the fourth minute the probe skirted bright grillwork like interlocking teeth, and sidestepped an umbrella-shaped piledriver that descended with crushing force. Eighty seconds later it stepped around a tilt-block that opened into a yawning abyss, deftly eluded a quintet of tetrahedal blades that sheared upward out of the pavement, and emerged onto a sliding walkway that carried it quickly forward for exactly forty seconds more.
All this had been traversed long ago by a Terran explorer named Cartissant, since deceased. He had dictated a detailed record of his experiences within the maze. He had lasted five minutes and thirty seconds, and his mistake had come in not getting off the walkway by the forty-first second. Those who had been monitoring him outside, back then, could not say what had happened to him after that.
As his drone left the walkway, Rawlins asked for another simulation and saw a quick dramatization of the computer’s best guess: the walkway opened to engulf its passenger at that point. The probe, meanwhile, was going swiftly toward what looked like the exit from this outermost zone of the maze. Beyond lay a well-lit, cheerful-looking plaza ringed with drifting blobs of a pearly glowing substance.
Rawlins said, “I’m into the seventh minute, and we’re still going, Charles. There seems to be a door into Zone G just ahead. Maybe you ought to cut in and monitor my screen.”
“If you last two more minutes, I will,” Boardman said.
The probe paused just outside the inner gate. Warily it switched on its gravitron and accumulated a ball of energy with a mass equivalent to its own. It thrust the energy ball through the doorway. Nothing happened. The probe, satisfied, trundled toward the door itself. As it passed through, the sides of the door abruptly crashed together like the jaws of a mighty press, destroying the probe. Rawlins’ screen went dark. Quickly he cut in one of the overhead probes; it beamed him a shot of his probe lying on the far side of the door, flattened into a two- dimensional mock-up of itself. A human being caught in that same trap would have been crushed to powder, Rawlins realized.
“My probe’s been knocked out,” he reported to Boardman. “Six minutes and forty seconds.”
“As expected,” came the reply. “We’ve got only two probes left. Switch over and watch.”
The master diagram appeared on Rawlins’ screen: a simplified and stylized light-pen picture of the entire maze as viewed from above. A small X had been placed wherever a probe had been destroyed. Rawlins found, after some searching, the path his own drone had taken, with the X marked between the zone boundaries at the place of the clashing door. It seemed to him that the drone had penetrated farther than most of the others, but he had to smile at the childish pride the discovery brought him. Anyhow, two of the probes were still moving inward. One was actually inside the second zone of the maze, and the other was cruising through a passageway that gave access to that inner ring.
The diagram vanished and Rawlins saw the maze as it looked through the pickup of one of the drones. Almost daintily, the man-high pillar of metal made its way through the baroque intricacies of the maze, past a golden pillar that beamed a twanging melody in a strange key, past a pool of light, past a web of glittering metal spokes, past spiky heaps of bleached bones. Rawlins had only glancing views of the bones as the drone moved on, but he was sure that few were human relics. This place was a galactic graveyard for the bold.
Excitement built in him as the probe went on and on. He was so thoroughly wedded to it now that it was as if he were inside the maze, avoiding one deathtrap after another, and he felt a sense of triumph as minutes mounted. Fourteen had elapsed now. This second level of the maze was not so cluttered as the first; there were spacious avenues here, handsome colonnades, long radiating passages leading from the main path. He relaxed; he felt pride in the drone’s agility and in the keenness of its sensory devices. The shock was immense and stinging when a paving-block upended itself unexpectedly and dumped the probe down a long chute to a place where the gears of a giant mill turned eagerly.
They had not expected that probe to get so far, anyway. The probe the others were watching was the one that had come in via the main gate—the safe gate. The slim fund of information accumulated at the price of many lives had guided that probe past all its perils, and now it was well within Zone G, and almost to the edge of F. Thus far, everything had gone as expected; the drone’s experiences had matched those of them who had tackled this route on earlier expeditions. It followed their way exactly, turning here, dodging there, and it was eighteen minutes into the maze without incident.
“All right,” Boardman said. “This is where Mortenson died, isn’t it?”
“Yes,” Hosteen answered. “The last thing he said was that he was standing by that little pyramid, and then he was cut off.”
“This is where we start gaining new information, then. All we’ve learned so far is that our records are accurate. This is the way in. But from here on—”
The probe, lacking a guidance pattern, now moved much more slowly, hesitating at every step to extend its network of data-gathering devices in all directions. It looked for hidden doors, for concealed openings in the pavement, for projectors, lasers, mass-detectors, power sources. It fed back to the central data banks all that it learned, thus adding to the store of information with each centimeter conquered.
It conquered, altogether, twenty-three meters. As the probe passed the small pyramid it scanned the broken body of the explorer Mortenson, lost at this point 72 years earlier. It relayed the news that Mortenson had been seized by a pressure-sensitive mangle activated by an unwary footstep too close to the pyramid. Beyond, it avoided two minor traps before failing to safeguard itself from a distortion, screen that baffled its sensors and left it vulnerable to the descent of a pulverizing piston.
“The next one through will have to cut off all its inputs until it’s past that point,” Hosteen muttered. “Running through blindfolded —well, we’ll manage.”
