The subway station, incrusted with its silent armies of stalactites and stalagmites, continued its drip, drip, drip. A haunting, maddening refrain. Wearily, Brent stood up and stretched his stiff, aching limbs. Dazed, he staggered to the sleek wet wall and cupped his hands to catch some of the falling water which ran down steadily from the enormous stalactite overhead. He drank. The water was fresh and cold. It felt good against his parched, sun-baked mouth. He let it dribble down his chin.

He watched the sleeping Nova, his mind tumbling again with imponderables, impossibilities and wild suppositions. He really didn’t know what to think. It was all so—so—incredible.

“Are you,” he asked the sleeping girl, “what we were before we learned to talk and made fools of ourselves? Did any good ever come of talking—round all those tables? Did apes make war when they were still dumb? Did men?”

Defeatedly, with of course no answer from the girl, he went over to a rocky vent in the station wall, through which some daylight feebly filtered, to look at the outside world from which he and Nova had escaped. He craned his neck to peer through.

He caught his breath, almost jumping back in terror.

About ten yards beyond the vent, he could see a veritable squad of gorilla guards, helmeted, armed, scouring the rocky maze, still obviously searching for him and the girl. He could make out the muttered concert of their ape voices. They didn’t sound very happy about something . . .

“I guess we lost them,” one of the fiercest-looking gorillas was growling to the others. “The sergeant says, keep looking. We’ve been here all night. The sergeant says we’d better not come back unless we’ve found them. Keep looking!”

Brent retreated from the vent, not wanting to see or hear any more. It was still unnerving seeing and hearing animals act like men. The same inflections, the same gestures . . .

He returned to Nova, bent over her, and gently roused her from sleep. She stirred fitfully, her long, curved body tensing.

“Nova, wake up!” he begged.

Instantly she opened her eyes and swung erect. He could see the rapid rise and fall of her semibared breasts within the ragged confines of her burlap-like garments. Her eyes searched his face. He forced a smile.

“We’ve got to keep moving,” he suggested. She nodded, her lips moistening nervously. He took her hand and swung her to her feet. He held onto her hand as he led her carefully down the long, dim, glistening subway platform with its mocking signs and depressing interior that spoke so eloquently of what had happened here many centuries before.

Suddenly he was aware of a faint humming sound.

Hummmmmmmmmmmmmmmmmmmmm . . .

He reacted. The girl did too.

He hadn’t been quite sure he hadn’t been hearing things but the awareness on Nova’s face was unmistakable.

“That hum. You hear it too!” He exulted, not knowing why. “We’re going to follow it . . .”

They did.

All along the platform, using the labyrinth of decayed track and seemingly endless tunnel as a guide. The hum grew gradually louder, with variations of volume and power so subtle that its tone didn’t increase abruptly. It merely increased, amplified as it were, to become a steady focus of attention. Excited, Brent clung to the girl, bringing her along behind him. The rhythmic hum and purr of the sound drew him on like a magnet. The tunnel seemed to lengthen, widen, and soon there was no more sign of the platform, the stalactites and stalagmites. None of the rotting, eroded fissures and cracks. The mouth of the cave ahead had rounded out, smoothened. Brent felt as if the way now led upward, that they would eventually surface somewhere in broad daylight in the outer world. But it was only illusion. The underground humming throbbed eerily, built symphonically, and now there was even a faint suggestion of a pleasant wind at their backs, wafting them onward, as if they were two vagrant feathers. It was totally unreal. With his ears filled with the vibrant hum of the unidentifiable noise, with all his senses riveted to an unknown force, Brent walked steadily forward, conscious only of movement and sound.

A long, slightly uphill passage loomed ahead of them.

Glimmering there, somewhere, was a high sliver of very dim light. Indirect light. The hum and the wind had both increased in velocity. They seemed to be hurled forward. Upward. The sliver of light was widening and even as they plummeted toward it, Brent could make out a rock-lined egress of some kind. The exit was just broad enough to accommodate both of them. Brent’s hair floated like a thatch on his head. Nova’s long tresses blew like pennants in the breeze. The hum had increased to dynamo intensity. It seemed to fill what was left of this world. The world of the desolate subway station had disappeared entirely.

Before them lay a high-vaulted, natural rock tunnel. With sleek, scaled, impossibly sheer sides. The light source proved to be another vent, set in the rock barrier across the uphill road’s dead end ten feet above the ground. Into it seemed to blow—or was it sucked, Brent thought wildly—the wind. From this issued the light. Too white to be the sky’s and yet . . .

“Whoever—or whatever—is guiding us to this place—” Brent muttered to the girl, “they breathe air, anyway.”

They drifted closer to the vent. Two black silhouettes starkly outlined against the bright, white light. The hum, like ten dynamos now, pulsated deafeningly.

Brent and Nova swept closer to the opening, to the weird vent with the weirder light.

He could see it was an octagonal frame, wrought in a white metal of some kind. He stared up at it speculatively, watching the wind rush through the opening. Grimly he got hold of himself. He began to climb toward the vent, putting his hand on the lowest bar of the metallic octagon to do so. Then a frightening thing happened. The electrical hum stopped, as quickly as if he had pushed a contact button. The sudden silence was terrifying.

Brent and the girl stood stock-still, stunned by the new quiet, the strange calm. Nova began to retreat, panicking.

“No,” Brent caught her. “It’s too late.” He drew her back again. “We’ve got to go on.”

But she pulled her hand free of his, shocked by the unknown. Rendered horrified by things she couldn’t understand. Brent tried to appeal to her, ignoring that she couldn’t follow his words.

“There’s a high intelligence at work in this place. Good or bad. That sound we heard is either a warning, or some kind of directional device. I don’t know which. But it doesn’t matter. The truth is—they know we’re here!”

She didn’t understand a word of it, of course, but his tone was so positive and reassuring that she almost smiled. But she continued to retreat, backing away slowly.

“All right,” Brent said. “I’ll go up first.”

And Brent continued his climb, while Nova watched anxiously. He hauled himself high enough up to grip the octagonal frame. He swung himself in, lost from view for a full second. Nova whimpered aloud. But his head reappeared, silhouetted against the vent. He beckoned. “Don’t be afraid. It’s empty. Come on.”

She reached up to him, climbing. He caught her hand and lifted her. He was very strong. Within seconds, he had swept her up from the strange world of the white tunnel, into the vent, and then they were both suddenly—standing in yet another maze of unreality. On the white floor of a white-walled, down-sloping tunnel, also octagonal in contour. The released air was funneling out of this down toward another white dot of far-off illumination. Another light of some kind. Brent did not hesitate. Pulling Nova, he led her toward the next outlet. The last exit to . . .

Where?

They emerged from the tunnel.

The glaring world of a new daylight invaded their aching eyes.