Presently the lights began to come up faintly. He guessed that Tickler stood behind the glass and heard the scream.

"Tickler," he called.

"Yes, sir?" His assistant's voice grated metallically through the overhead speakers.

"Did I scream just now?"

"I'm sorry?"

"Did you hear anything unusual-a scream, a yell? Anything like that?"

"When, Dr. Reston?"

"Just now. When I woke up."

"No, sir. The alarm went off in the control booth, so I turned on the lights. That is the procedure."

"You're quite right. Thank you." His heart was still beating rapidly. He could feel the tension in his shoulders and neck. His hands still clutched the sides of the cav couch in a death grip. He felt certain the scream had been real, that it was not merely part of his dream.

But why would Tickler lie about a thing like that? Perhaps he had not been in the booth when Spence screamed, or perhaps he was covering up the fact that he had himself dozed off at his post. Possibly. But it was not like Tickler.

Spence rose and stretched and made his way into the control room. Tickler was just winding the scan onto a spool. Spence watched him finish and place a seal on the loose end.

"Will that be all for now?" Tickler asked.

"Yes; you may go. I won't be needing anything further this shift, but tell Kurt when he comes in that I'd like the log posted and I'd like to see the averages for the last three sessions."

"The averages?"

"Yes. Just as soon as he gets them finished."

"But we have never-"

"Don't argue, Tickler. Please, just do as I say. I know it's a little extra work. But that's what we have an assistant for, isn't it?"

"Very well, I'll tell him."

Tickler turned brusquely and went out. I wonder what's eating him this time? With Tickler it was always something.

Spence brushed the thought from his mind and left the control booth, crossed the lab, and entered his quarters. Despite the night's sleep he did not feel at all rested. He felt as though he had run several miles or climbed a sheer rock cliff. His muscles were tense and knotty and he could smell that he had sweated through his underclothes.

He thought to sanitize and change, but then had a better idea: the exerdome. Why not? He could use the exercise. Maybe he would find a threesome who needed a fourth for a game of pidg.

As he donned his silvered mylar exersuit it occurred to him that perhaps his problems stemmed from stress and overwork. He had exercised little since coming to Gotham; except for his occasional rambles through the garden and a swim now and then, he had indulged in no physically strenuous activity. A fast game of pidg or a few laps around the dome would loosen him up and relax him.

He took a main axial to the low-gray central tower of the city. Nearly weightless, he sprang four meters from the corridor to the lift and stepped onto a disc, pulling up the handgrips as it engaged the belt. Up he rose to the dome. He could hear laughter and shouts pinging down the metal tube from above. It reminded him of going swimming as a boy and hearing the sounds of happy frolic ringing from the pool a long way off.

When the lift gate opened he stepped off onto the spongy surface of the dome-or rather bounced off with the first step, for he was now completely weightless. He spun awkwardly for a moment before remembering to pull in his arms and legs to regain control. He brought his knees up to his chest and, when he floated near enough to the curved surface once again, thrust his legs down. He arrowed off the side of the dome and flew straightway toward the center. High above him a net stretched across the observation portion of the dome to keep errant human missiles from colliding with the tempered glass.

Beyond the netting he could see a bright mist of stars hanging in their inky void. Lower, he could see the upside-down crescent of the moon and the smaller blue thumbnail slice of the Earth. Spence flew into the netting, tucked his head down, and landed on his back. He pulled himself across the net to a near wall.

Above him a group of cadets performed an intricate display of aerial acrobatics-doing flips and somersaults across the center of the dome. Around the perimeter several joggers sped along the track; another group ran perpendicular to the first. A couple of fluffy pidg birds floated down near the lift platform. No one seemed interested in getting up a game, so Spence swam to the edge of the net and walked up the great bulging sphere of the dome to the red strip designated as the track.

The track's surface bore a slightly irregular, bumpy grain which gave a runner that little extra bit of traction needed to get moving in zero gravity. Spence carefully set his feet on the track and then started walking smoothly, with exaggerated care; one false step and he would go spinning off toward the center of the dome. But he maintained his concentration and increased the pace, feeling the illusion of weight return to him. Actually it was only momentum he felt, and which held him to the track. Soon he was running easily around the inner wall of the dome.

He caught the other joggers on the track and fell into pace with them. In the rhythm of running his muscles relaxed and the tension flowed from him. Automatically his body took over and his mind turned once again to the enigma of his dreams.

That he dreamed was certain. His REM line on the scan showed plainly what he knew instinctively, and if he required further proof the emotional residue-that silt left behind when the angry waters had raced on-was real enough. Not to remember a dream was normal enough; one remembered only the tiniest fraction of one's dreams over a lifetime. They simply flitted by in the night-spun out of the stuff of the subconscious and reabsorbed into the fabric of the psyche upon waking.

But blackouts were not normal. Spence felt as if whole chunks of his life were missing. There were gaps in his memory which he could not cross, dark curtains behind which he could not see. That scared him.

More than the nightmares, more than the cargo bay incident, he feared the helplessness, the utter defenselessness of not knowing what was happening to him. The carefully reasoned and researched framework of his life teetered precariously, threatening to topple completely, and he did not know what to do about it.

He lowered his head and spurted past the others. His lungs burned and sweat stung his eyes, but he continued running faster and faster as if to escape the fear which came swimming out of the darkness of the star-spangled night beyond the netting. Closing his eves he thrust the fear from him as if it were a solid object he could throw aside. …

AFTER HIS RUN SPENCE lay motionless in the center of the dome, turning slowly on his own axis like a minor planet. The warm glow of exertion throbbed through his limbs. He had reached that blissful state of exhaustion where body and spirit were reconciled one to the other and the universe hummed with peace.

He listened to the play of others and watched through halfclosed lids as the red line of the track circled him aimlessly. It was, he thought, a tribute to the supreme egotism of the mind that he seemed completely stationary while the entire space city of Gotham revolved around him. Around and around it went, spinning in its own lazy orbit-now the black mirror of the observation bubble, now the red line of the track.

The red line of the track. Something about that seemed important. Spence jerked his head up and sent himself floundering away at an obtuse angle. In the same instant it came to him: the red line of the track was the red line of his sleep scan. He had meant to check it, but had forgotten, or the thought had been driven from his mind by the circumstances of his latest blackout.

Suddenly it seemed more important than ever. He dove for the nearest wall and then propelled himself toward the lift platform. He raced back to the lab with his heart pounding and the certainty drumming in his brain that he was very close to finding an answer to the riddle of his dreams.