Touched and saddened by all that evidence of Mansfield's austere innocence, Forester turned slowly back to watch the inner door, Jane Carter's anxious hand cold and tiny in his own.
"First we must find those two sections - number four and number five." His mind was rehearsing the steps they must take to undo that unintended crime.
"You must keep watch while I unhook them, and then bring me the new sections from the cave.
I'll hook them in - and you must stop any humanoid that finds us."
Listening, she nodded.
That would take them no more than another five minutes - to amend the Prime Directive with a bill of human rights, and free many thousand worlds from a suffocating kindness.
Unless men blundered again.
His heart began to thump as Jane Carter tightened her icy fingers in his hand, nodding silently at the inner door.
That door also had a common knob, and no concealed relay.
He opened it cautiously - to close it very quickly.
For he had seen the grid.
Its limitless billions of tiny palladium relays, the cells of the mechanical brain, were all linked with the rhodomagnetic synapses in sections like the two he had built.
The sections were arranged in long panels, all connected with a coiling jungle of branching wave-guide tubes of white palladium, the panels mounted in a skeleton of massive columns and girders that seemed to have no end.
The humanoids required no light, and most of that enormous space inside the tower was dark.
On this original level, however, which Warren Mansfield himself had designed and begun, the panel faces and the narrow inspection walks before them were finished with a gray- glowing paint, whose dim radiance shone far into the gloom, above and beyond and below.
Rooms to hold the precise mind and unerring memory of all the far-scattered moving units, the panels of the grid made endless shadowy avenues, rising level upon level as far as he could see, and falling away, level beneath unending level, into the chasm of whispering dark.
"What's wrong?" Jane breathed fearfully.
It was the humanoids, the busy limbs of that eternal brain.
He had seen scores of the tiny- seeming mechanicals moving with their swift, efficient grace about the web of narrow walks strung through the dim abyss between the tiers of panels.
The nearest one, poised on a thin footway not fifty yards distant, had been facing toward him, and terror of its bright steel eyes had stricken him.
He leaned weakly against the closed door, speechless.
"But it didn't see you, Dr. Forester," Jane whispered through her own pale alarm.
"It can't really see, you know, and Mr. White says it can't feel us more than about ten paces, here in the tower.
He says it's only working with the others to clean and keep up the grid."
"I'm sorry." He moved shakenly to open the door again. "I just forgot they're blind."
They crept out silently, into the vast chamber of the brain.
Beneath a soundless hush, Forester fancied that he could feel the pulsation of unimaginable energies - the rivers of incalculable rhodomagnetic power that flowed out from here to drive and control all the trillions of mechanicals serving all the worlds that men had owned.
Following a narrow, dim-lit catwalk that had no railing - because it was built for perfect machines, that never slipped or stumbled - he searched the gray glowing panel faces.
And he found the numbers old Mansfield had painted on the sections, eighty years ago. Hasty brush marks, splashed on merely for identification in the shop, they were faded now, peeling away from the satiny palladium shieldings. But he could read them still.
The first three sections held the Prime Directive.
Three long, silver-gray cases, a little smaller than three coffins.
The freedom and the future of mankind had lain buried in them for eighty years, he thought, murdered by Mansfield's error to preserve a sterile peace.
He passed them and crept on toward those beyond, the silent child clinging hard to his arm.
Trying to ignore the blind machines ahead, trying to forget the giddy pit beneath, he leaned to read the faded numbers.
Four!
For an instant he couldn't breathe.
He felt as if that narrow walk had swayed beneath him, and he had to clutch desperately for a flange of the nearest massive girder.
But he got his balance back, and he was fumbling desperately to open the little leather case of tools he had brought to change the connections, when he felt Jane tugging sharply at his hand.
Turning apprehensively, he saw her pointing at that nearest black mechanical.
It was still busy removing invisible dust from the panel faces with something like a tiny, silent vacuum cleaner, but it was working steadily toward them.
Forester saw that he had no time for terror.
He found his pliers and lifted the cover of the fourth section and began rapidly unhooking the flexible wave-guide tubes that coupled it into the brain.
"Oh-"
Jane Carter's cry was a low and stifled moan of pain.
She let his fingers go, but at first he didn't know what had happened.
He thought she was falling from the walk until he saw her backing silently away from him along it, and then he thought that nearest humanoid must have discovered them.
His dropped pliers made a frightening clatter on the metal shielding.
He almost lost his own balance, and skinned his knuckles on the sharp edge of the section cover in his frantic snatch for safety.
That busy machine was still approaching as it dusted the panels, but he saw in a moment that it hadn't yet found them.
He looked back down at Jane, trying to see what had so disturbed her.