On the uppermost levels of some of the wealthiest subsections of the City are the natural Solariums, where a partition of quartz with a movable metal shield excludes the air but lets in the sunlight. There the wives and daughters of the City's highest administrators and executives may tan themselves. There a unique thing happens every evening.

Night falls.

In the rest of the City (including the UV-Solariums, where the millions, in strict sequence of allotted time, may occasionally expose themselves to the artificial wavelengths of arc lights) there are only the arbitrary cycles of hours.

The business of the City might easily continue in three eight-hour or four six-hour shifts, by "day" and "night" alike. Light and work could easily proceed endlessly. There are always civic reformers who periodically suggest such a thing in the interests of economy and efficiency.

The notion is never accepted.

Much of the earlier habits of Earthly society have been given up in the interests of that same economy and efficiency: space, privacy, even much of free will. They are the products of civilization, however, and not more than ten thousand years old.

The adjustment of sleep to night, however, is as old as man: a million years. The habit is not easy to give up. Although the evening is unseen, apartment lights dim as the hours of darkness pass and the City's pulse sinks. Though no one can tell noon from midnight by any cosmic phenomenon along the enclosed avenues of the City, mankind follows the mute partitionings of the hour hand.

The expressways empty, the noise of life sinks, the moving mob among the colossal alleys melts away; New York City lies in Earth's unnoticed shadow, and its population sleeps.

Elijah Baley did not sleep. He lay in bed and there was no light in his apartment, but that was as far as it went.

Jessie lay next to him, motionless in the darkness. He had not felt nor heard her move.

On the other side of the wall sat, stood, lay (Baley wondered which) R. Daneel Olivaw.

Baley whispered, "Jessie!" Then again, "Jessie!"

The dark figure beside him stirred slightly under the sheet. "What do you want?"

"Jessie, don't make it worse for me."

"You might have told me."

"How could I? I was planning to, when I could think of a way. Jehoshaphat, Jessie - "

Baley's voice returned to its whisper. "How did you find out? Won't you tell me?"

Jessie turned toward him. He could sense her eyes looking through the darkness at him.

"Lije." Her voice was scarcely more than a stirring of air. "Can he hear us? That thing?"

"Not if we whisper."

"How do you know? Maybe he has special ears to pick up tiny sounds. Spacer robots can do all sorts of things."

Baley knew that. The pro-robot propaganda was forever stressing the miraculous feats of the Spacer robots, their endurance, their extra senses, their service to humanity in a hundred novel ways. Personally, he thought that approach defeated itself. Earthmen hated the robots all the more for their superiority.

He whispered, "Not Daneel. They made him human-type on purpose. They wanted him to be accepted as a human being, so he must have only human senses."

"How do you know?"

"If he had extra senses, there would be too much danger of his giving himself away as non-human by accident. He would do too much, know too much."

"Well, maybe."

Silence fell again.

A minute passed and Baley tried a second time. "Jessie, if you'll just let things be until - until... Look, dear, it's unfair of you to be angry."

"Angry? Oh, Lije, you fool. I'm not angry. I'm scared; I'm scared clean to death."

She made a gulping sound and clutched at the neck of his pajamas. For a while, they clung together, and Baley's growing sense of injury evaporated into a troubled concern.

"Why, Jessie? There's nothing to be worried about. He's harmless. I swear he is."

"Can't you get rid of him, Lije?"

"You know I can't. It's Department business. How can I?"

"What kind of business, Lije? Tell me."

"Now, Jessie, I'm surprised at you." He groped for her cheek in the darkness and patted it. It was wet. Using his pajama sleeve, he carefully wiped her eyes.

"Now, look," he said tenderly, "you're being a baby."

"Tell them at the Department to have someone else do it, whatever it is. Please, Lije."

Baley's voice hardened a bit. "Jessie, you've been a policeman's wife long enough to know an assignment is an assignment."

"Well, why did it have to be you?"

"Julius Enderby - "

She stiffened in his arms. "I might have known. Why can't you tell Julius Enderby to have someone else do the dirty work just once. You stand for too much, Lije, and this is just - "

"All right, all right," he said, soothingly.

She subsided, quivering.

Baley thought: She'll never understand.

Julius Enderby had been a fighting word with them since their engagement. Enderby had been two classes ahead of Baley at the City School of Administrative Studies. They had been friends. When Baley had taken his battery of aptitude tests and neuroanalysis and found himself in line for the police force, he found Enderby there ahead of him. Enderby had already moved into the plain-clothes division.

Baley followed Enderby, but at a continually greater distance. It was no one's fault, precisely. Baley was capable enough, efficient enough, but he lacked something that Enderby had. Enderby fit the administrative machine perfectly. He was one of those persons who was born for a hierarchy, who was just naturally comfortable in a bureaucracy. The Commissioner wasn't a great brain, and Baley knew it. He had his childish peculiarities, his intermittent rash of ostentatious Medievalism, for instance. But he was smooth with others; he offended no one; he took orders gracefully; he gave them with the proper mixture of gentleness and firmness. He even got along with the Spacers. He was perhaps over-obsequious to them (Baley himself could never have dealt with them for half a day without getting into a state of bristle; he was sure of that, even though he had never really spoken to a Spacer), but they trusted him, and that made him extremely useful to the City. So, in a Civil Service where smooth and sociable performance was more useful than an individualistic competence, Enderby went up the scale quickly, and was at the Commissioner level when Baley himself was nothing more than a C-5. Baley did not resent the contrast, though he was human enough to regret it. Enderby did not forget their earlier friendship and, in his queer way, tried to make up for his success by doing what he could for Baley.

The assignment of partnership with R. Daneel was an example of it.

It was tough and unpleasant, but there was no question that it carried within it the germs of tremendous advance. The Commissioner might have given the chance to someone else. His own talk, that morning, of needing a favor masked but did not hide that fact.

Jessie never saw things that way. On similar occasions in the past, she had said, "It's your silly loyalty index. I'm so tired of hearing everyone praise you for being so full of a sense of duty. Think of yourself once in a while. I notice the ones on top don't bring up the topic of their own loyalty index."

Baley lay in bed in a state of stiff wakefulness, letting Jessie calm down. He had to think. He had to be certain of his suspicions. Little things chased one another and fitted together in his mind. Slowly, they were building into a pattern.

He felt the mattress give as Jessie stirred.

"Lije?" Her lips were at his ear.

"What?"

"Why don't you resign?"

"Don't be crazy."

"Why not?" She was suddenly almost eager. "You can get rid of that horrible robot that way. Just walk in and tell Enderby you're through."

Baley said coldly, "I can't resign in the middle of an important case. I can't throw the whole thing down the disposal tube just any time I feel like it. A trick like that means declassification for cause."

"Even so. You can work your way up again. You can do it, Lije. There are a dozen places where you'd fit into Service."

"Civil Service doesn't take men who are declassified for cause. Manual labor is the only thing I can do; the only thing you could do. Bentley would lose all inherited status. For God's sake, Jessie, you don't know what it's like."

"I've read about it. I'm not afraid of it," she mumbled.

"You're crazy. You're plain crazy." Baley could feel himself trembling. There was a familiar, flashing picture of his father in his mind's eye. His father, moldering away toward death.

Jessie sighed heavily.

Baley's mind turned savagely away from her. In desperation, it returned to the pattern it was constructing.

He said, tightly, "Jessie, you've got to tell me. How did you find out Daneel was a robot? What made you decide that?"

She began, "Well..." and just ran down. It was the third time she had begun to explain and failed.

He crushed her hand in his, willing her to speak. "Please, Jessie. What's frightening you?"

She said, "I just guessed he was a robot, Lije."

He said, "There wasn't anything to make you guess that, Jessie. You didn't think he was a robot before you left, now did you?"

"No-o, but I got to thinking..."

"Come on, Jessie. What was it?"

"Well - Look, Lije, the girls were talking in the Personal. You know how they are. Just talking about everything."

Women! thought Baley.

"Anyway," said Jessie. "The rumor is all over town. It must be."

"All over town?" Baley felt a quick and savage touch of triumph, or nearly that. Another piece in place!

"It was the way they sounded. They said there was talk about a Spacer robot loose in the City. He was supposed to look just like a man and to be working with the police. They even asked me about it. They laughed and said, 'Does your Lije know anything about it, Jessie?' and I laughed, and said, 'Don't be silly!'

"Then we went to the etherics and I got to thinking about your new partner. Do you remember those pictures you brought home, the ones Julius Enderby took in Spacetown, to show me what Spacers looked like? Well, I got to thinking that's what your partner looked like. It just came to me that that's what he looked like and I said to myself, oh, my God, someone must've recognized him in the shoe department and he's with Lije and I just said I had a headache and I ran - "

Baley said, "Now, Jessie, stop, stop. Get hold of yourself. Now why are you afraid? You're not afraid of Daneel himself. You faced up to him when you came home. You faced up to him fine. So - "

He stopped speaking. He sat up in bed, eyes uselessly wide in the darkness.

He felt his wife move against his side. His hand leaped, found her lips and pressed against them. She heaved against his grip, her hands grasping his wrist and wrenching, but he leaned down against her the more heavily.

Then, suddenly, he released her. She whimpered.

He said, huskily, "Sorry, Jessie. I was listening."

He was getting out of bed, pulling warm Plastofilm over the soles of his feet.

"Lije, where are you going? Don't leave me."

"It's all right. I'm just going to the door."

The Plastofilm made a soft, shuffling noise as he circled the bed. He cracked the door to the living room and waited a long moment. Nothing happened. It was so quiet, he could hear the thin whistle of Jessie's breath from their bed. He could hear the dull rhythm of blood in his ears.

Baley's hand crept through the opening of the door, snaking out to the spot he needed no light to find. His fingers closed upon the knob that controlled the ceiling illumination. He exerted the smallest pressure he could and the ceiling gleamed dimly, so dimly that the lower half of the living room remained in semidusk.

He saw enough, however. The main door was closed and the living room lay lifeless and quiet.

He turned the knob back into the off position and moved back to bed.

It was all he needed. The pieces fit. The pattern was complete. Jessie pleaded with him. "Lije, what's wrong?"

"Nothing's wrong, Jessie. Everything's all right. He's not here."

"The robot? Do you mean he's gone? For good?"

"No, no. He'll be back. And before he does, answer my question."

"What question?"

"What are you afraid of?" Jessie said nothing.

Baley grew more insistent. "You said you were scared to death."

"Of him."

"No, we went through that. You weren't afraid of him and, besides, you know quite well a robot cannot hurt a human being."

Her words came slowly. "I thought if everyone knew he was a robot there might be a riot. We'd be killed."

"Why kill us?"

"You know what riots are like."

"They don't even know where the robot is, do they?"

"They might find out."

"And that's what you're afraid of, a riot?"

"Well - "

"Sh!" He pressed Jessie down to the pillow.

Then he put his lips to her ear. "He's come back. Now listen and don't say a word. Everything's fine. He'll be gone in the morning and he won't be back. There'll be no riot, nothing."

He was almost contented as he said that, almost completely contented. He felt he could sleep.

He thought again: No riot, nothing. And no declassification. And just before he actually fell asleep, he thought: Not even a murder investigation. Not even that. The whole thing's solved...

He slept.