A nondescript living room. A female shadow. She threw up her hands and stood transfixed for a horrible moment or two. A male shadow bounded into the picture—a giant male shadow. She turned to run, and he caught her from behind. His hand moved upward. Something glittered in it, and he brought it down. He struck twice, and the female crumpled to the floor. He whirled, ran toward us, and disappeared. The camera ground on, recording the image of that shapeless shadow on the floor.

Abruptly the scene changed. A restaurant, with crowded tables and jerkily moving robot-servers. Walker swore softly and turned off the camera.

"That's all I got before," he said. "If I could come on it from a different angle, maybe we could locate the place."

"When?" the Captain asked.

"Seven to twelve days."

It hit me, then, like a solid wallop on the jaw. I'd been looking into the future.

"Plenty of time," the Captain said. "But not much to go on." He looked at me. "What do you think?"

"Might be able to identify the man," I said. "He'll be well over six feet—wouldn't surprise me if he were six-eight or nine. He'll have the build of a male gorilla. And he limps slightly with his right foot."

"Not bad. Anything else?"

"It's an apartment or a hotel room," I said. "I'd guess an apartment. The scanner screen by the door means it's either relatively new, or it's been remodeled. The living room has a corner location, with windows on two sides. It's hard to say for certain, but I believe there's an old-fashioned sofa—one of those with a back on it—along the far wall."

Walker slumped into a chair. "You make me feel better," he said. "I thought there was next to nothing to go on."

Captain Marks nodded. "But you missed one thing."

"What's that?"

"Our assailant is left-handed. Also—the limp may be something temporary. All right, Forsdon, it's all yours. Seven to twelve days, and you'd better plan on seven."

He went back to his office, and I looked at Walker. "Can you give me any idea at all as to the location?"

"I can draw you a circle on the map, but it's only about fifty-fifty that you'll find the place inside the circle."

"That's better than nothing."

"There is one thing," Walker said. "I'd like to have you wear this. Everywhere."

A band of elastic, with what looked like dark beads placed on it at intervals.

"It's an arm band," Walker said. "Cronus picks up these beads as bright spots. So I'll be able to identify you if you show up on the screen."

I hesitated, and he said, "The Captain wears one. We know it works, because Cronus has picked him up twice."

I took the arm band, and slipped it on.

I sat down with the map and a directory and worked until a technician came back with the developed film. Walker was still perspiring in front of Cronus. He hadn't been able to focus on the crime a third time. The Captain's door was closed, and his nasal voice was rattling the door as he bellowed into his telephone. I pulled the curtains to darken one corner of the room, and fed the film into a projection machine.

I ran the film ten times without coming up with anything new. I couldn't make out the number on the door. I also couldn't decide whether the assailant was a chance prowler or someone known to the victim. I stopped the camera, and made a sketch of the room from what I could make out in the way of furnishings.

The Captain came barging out of his office, took a quick look at my sketch, and nodded approval. "We'll find the apartment," he said. "Then our troubles will really start."

I couldn't see that, and I told him so. I figured our troubles would be nearly over if we found the apartment.

"You think it's possible to prevent this crime," he said. "I don't. Even if we find the apartment and identify the man and woman, the crime is still going to happen."

"Why?" I said.

"Look at it this way. If we prevent the crime, it's not going to happen. Right?"

"Right."

"And if it's not going to happen, Cronus wouldn't show it to us. All you see on that screen is what will happen. As far as Cronus is concerned, it already has happened. Preventing it is like trying to change the past."

"We can try," I said.

"Yes, we can try. The regular force will help us on this one. A team of detectives is waiting outside. Tell them what you want done."

I wanted an apartment living room with a corner location and a door scanner. It wasn't as bad as it sounded—the scanner was a new gadget at that time. Not many apartment buildings would have it. There was always the chance, of course, that an individual had had one installed on his own, but that was a worry I could postpone.

I put in a hectic day of trudging through apartment buildings and squabbling with superintendents, but we found it the next morning, in a stubby little seven-story building on South Central. It was one of those apartment buildings that went up way back in 1990, when the city decided it couldn't afford the luxury of open spaces and opened part of old Central Park to apartment buildings. This one was a midget among the other buildings in that development, but it had been remodeled recently. It had scanner screens.

After the usual protests, the superintendent showed me around. Most of the occupants weren't home. He let me into a rear apartment on the sixth floor, and I took one look and caught my breath.

I pulled out my sketch, though I had it memorized by this time, and moved across the room to get the right angle. The sofa was there—it was an old-fashioned job with a back. What had been a bright blotch in the picture turned out to be a mirror. A blur by the sofa was a low table. A chair was in the wrong place, but that could have been moved. What was I thinking about? It was going to be moved. Every detail checked.

"Stella Emerson," the superintendent said. "Miss Stella Emerson—I think. She never gave me no trouble. Something wrong?"

"Not a thing," I said. "I want some information from her."

"I dunno when she's home."

Her next-door neighbor did. I went back to headquarters and picked up the loose ends on the attempt to identify our assailant-to-be. No luck.

And at six o'clock that evening, I was having a cup of coffee with Miss Stella Emerson.

She was the sort of person it's always a joy to interview. Alert, understanding, cooperative—none of that petty, temperamental business about invasion of privacy. She was brunette and twenty-six or twenty-seven, maybe five feet four, a hundred and ten pounds. The pounds were well distributed, and she was darned nice looking.

She served the coffee on the low table by the sofa, and sat back with her cup in her hand.

"You wanted information?" she said.

I fingered my own cup, but I didn't lift it. "I'd like to have you think carefully," I said, "and see if you've ever known a man who matches this description. He's big, really big. Heavy set. Maybe six feet eight or nine. He's left handed. He might walk with a slight limp in his right foot...."

She set her cup down with a bang. "Why, that sounds like Mike—Mike Gregory. I haven't seen him for years. Not since...."

I took a deep breath, and wrote "Mike Gregory" in my notebook.

"Where was he when you saw him last?"

"On Mars. I was there for two years with Civil Service. Mike was a sort of general handyman around the administration building."

"Do you know where he is now?"

"As far as I know, he's still on Mars!"

My coffee was scalding hot, but I didn't notice as I gulped it down. "I'd like to know everything you can tell me about this Mike Gregory," I said. "May I take you to dinner?"

As my dad used to say, there's nothing like mixing business with pleasure.

She suggested the place—a queer little restaurant in the basement of a nearby apartment building. There were lighted candles on the tables—the first candles I'd seen since I was a child. The waitresses wore odd costumes with handkerchiefs wrapped around their heads. An old man sat off in one corner scraping on a violin. It was almost weird.

But the food was good, and Stella Emerson was good company. Unfortunately, her mind was on Mike Gregory.

"Is Mike in trouble?" she said. "He always seemed like such a gentle, considerate person."

I thought of the knife-wielding shadow, and shuddered. "How well did you know him?" I said.

"Not too well—he stopped to talk with me now and then. I never saw him except at work."

"Was he—interested in you?"

She blushed. It was also the first blush I had seen in so long I couldn't remember when. I had heard it said that the blush went out when women did away with their two-piece bathing suits and started wearing trunks like the men. I'm telling you, you can't have any idea about what's wrong with our scientific civilization until you've seen a girl blush by candlelight.

"I suppose he was," she said. "He kept asking me to go places with him. I felt sorry for him—he seemed such a grotesque person—but I didn't want to encourage him."

"You're certain about the limp?"

"Oh, yes. It was very noticeable."

"And about his being left-handed?"

She thought for a moment. "No. I'm not certain about that. He could have been, I suppose, but I don't think I ever noticed."

"Is there anything else you remember about him?"

She shook her head slowly. "Not much, I'm afraid. He was just a person who came through the office now and then. He had an odd way of talking. He spoke very slowly. He separated his words, just ... like ... this. Most of the girls laughed at him, and when they did he'd turn around and walk away without saying anything. And—oh, yes, sometimes he'd talk about California. I guess that was where he was from. I never found out anything about his personal life."

"But you didn't laugh at him?"

"No. I couldn't laugh at him. He was just too—pathetic."

"Have you heard from him since you came back?"

"He sent me a Christmas card once. He didn't know my address on Earth, so he sent it to the office on Mars so it would be forwarded. It didn't reach me until July!"

"How long ago was that?"

"It must be four years ago. It was a couple of years after I left Mars."

I dropped Mike Gregory, and tried to learn something about Stella Emerson.

She was twenty-eight. She'd worked for two years on Mars, and then she came back and got a job as private secretary with a small firm manufacturing plastic textiles. She made enough money for her own needs, and was able to save a little. She liked having a place of her own. She had a sister in Boston, and an aunt over in Newark, and they visited her occasionally. She led a quiet life, with books, and visits to the art institutes, and working with her hobby, which was photography.

It all sounded wonderful to me. The quiet life. A detective gets enough excitement on the job. If he can't relax at home, he's going to be a blight on the mortality tables.

We were on our second cup of coffee, by then, and I motioned the old fiddler over to our table.

His bloodshot eyes peered out ever a two-week growth of beard. I slipped him a dollar bill. "How about giving us a melody."

He gave us a clumsy serenade and Stella reacted just as I'd hoped she would. She blushed furiously, and kept right on blushing, and I just leaned back and enjoyed it.

I took her back to her apartment, and said a friendly farewell at her door. We shook hands!

And she didn't invite me to spend the night with her, which was just as refreshing.

I rode the elevator with chiming bells and a wisp of the old man's music floating through my mind. I stepped out on the ground level, walked dreamily out the door and hailed an aircab with my pocket signal.

And just as I was about to step in, it stabbed me like the flickering knife on Cronus's screen. She was a wonderful girl, and I was falling for her, and in seven to twelve days—no, nearer five to ten days, now—she was going to be murdered.

"Something wrong?" the driver said.

I flashed my credentials. "Police Headquarters," I said. "Use the emergency altitude."

Walker was crouched in front of Cronus, perspiring, as usual, but looking infinitely more tired. No matter what time I came in, he always seemed to be there, or there was a note saying he was down in his lab in the sub-basement.

"I haven't found it again," he said.

"That's all right. We can manage with what we have."

He frowned irritably. "It's important, confound it. This is just an experimental model, and it's maddeningly inefficient. With money and research facilities, we could produce one that would really work, but we can't get that kind of support by predicting a few piddling holdups. But a murder, now—that would make someone sit up and take notice."

"Stop worrying about your dratted Cronus," I snapped. "I don't give a damn about that pile of junk. There's a girl's life to be saved."

It was unfair, but he didn't object. "Yes, of course," he said. "The girl's life—but if I can't get more information...."

"I've found the apartment," I told him, "and I've found the girl. But the man is supposed to be on Mars. It doesn't figure, but it's something to work on."

I called the Captain, and gave him my report. If he resented my bothering him at home, he didn't show it. Any wheel I could get my fingers on I set turning, and then I went home. I won't pretend that I slept.

By morning we had a complete report from the colonial administration on Michael Rolland Gregory. Fingerprints, photos, detailed description, complete with limp and left-handedness. The works. Also, the added information that he'd resigned his civil service job eight months before and had left immediately for Earth, on a Dawn Liner scheduled to land at San Francisco.

I swore savagely, got off an urgent message to San Francisco, and left for a dinner date with Stella Emerson. And another handshake at her apartment door.

San Francisco did a thorough job, but it took time—two more days. Michael Rolland Gregory had hung around for a while, living in run-down rooming houses, and holding a series of odd jobs. Two months before he had disappeared.

"He could be anywhere by now," I told the Captain.

"Including here in New York," the Captain said dryly.

Two to seven days.

I took Stella back to her apartment after our dinner date, and in front of the door I said, "Stella, I like you."

She blushed wonderfully. "I like you too, Jim."

"Then do me a favor—a very special favor."

Her blush deepened, with an overlay of panic. "I'd—like to, Jim. Because I—like you. But I can't. It's hard to explain, but I've always told myself that unless I marry a man...."

I leaned against the wall and laughed helplessly while her eyes widened in amazement. Then I dispensed with the handshaking. She clung to me, and it might have been her first kiss. In fact, it was.

"I don't just like you, darling," I said. "I love you. And that wasn't the favor I was going to ask. You said you have an aunt over in Newark. I want you to stay with her for a while—for a week or so."

"But—why?"

"Will you trust me? I can't tell you anything except that you're in danger here."

"You mean—Mike?"

"I'm afraid so."

"It's hard to believe that Mike would want to harm me. But if you think it's important...."

"I do. Will you call your aunt, now, and make the arrangements? I'll take you over tonight."

She packed some things, and I took her to Newark in an aircab. Her aunt was hospitable and cooperative, albeit a little confused. I checked her apartment thoroughly. I was taking no chances that the aunt's living room could be the potential scene of the crime. It wasn't—no similarity.

"Promise me," I said, "that you won't go back to your apartment for any reason until I tell you it's all right."

"I promise. But I may need some more things."

"Make a list, and I'll have a police woman pick them up for you."

"All right."

I arranged with the superintendent of her apartment building to have the lights in her apartment turned on each evening, and turned off at an appropriate time. I put a stakeout on her apartment building, and on her aunt's. I got a detective assigned to shadow her, though she didn't know it, of course. Then it was zero to five days, and I was quietly going nuts.

Zero to four days. I walked into the D. F. C. room, and Walker swarmed all over me. "I found it again," he said.

"Anything new?"

"No. Just the same thing. Exactly the same."

"When?"

"Two to three days."

I sat down wearily, and stared at Cronus. The screen was blank. "How did you manage to invent that thing?" I said.

"I didn't really invent it. I just—discovered it. I was tinkering with a TV set, and I changed some circuits and added a lot of gadgets, just for the hell of it. The pictures I got were darned poor, but they didn't seem to be coming from any known station—or combination of stations, since they kept changing. That was interesting, so I kept working on it. Then one day the screen showed me a big aircar smashup. There were about ten units involved, and I told myself, 'Boy, these Class D pictures are really overdoing it.' About a week later I opened my morning paper, and there was the same smashup on page one. It took a long time to get anybody interested."

He stopped suddenly as the Captain came charging out of his office.

"Brooklyn," he called. "Gregory was living in a rooming house in Brooklyn. He left three weeks ago."

A lead with a dead end. No one knew where he'd gone. It proved that he was somewhere in the vicinity of New York City, but I don't think any of us ever doubted that.

"One thing is interesting," the Captain said. "He's using his own name. No reason why he shouldn't, of course. He's not a criminal—but he is a potential criminal, and he doesn't know that."

I saw, suddenly, that we had a double problem. We had to protect Stella from Gregory, but we also had to protect Gregory from himself. If we could find him.

"There's not much we can do," I said, "but keep on looking."

It was what Walker called the Critical Period. Something had to happen on this day or the next, or Cronus was a monkey's dutch uncle.

"If we could only pick Gregory up and hold him for a couple of days, maybe we could beat this," I told the Captain. "We've eliminated Stella Emerson, we've locked the apartment, and caging Gregory should snap the last thread."

He laughed sarcastically. "You think that would solve the problem? Listen. We spotted a holdup, and I recognized the crook. He had a long record. I had him picked up, and he was carrying a gun so we slapped him in jail on a concealed weapons charge. He escaped, got another gun, and committed the holdup right on schedule. I'm telling you, Cronus shows exactly how the future is. We can't change it. I'm working as hard as anyone else to prevent this, but I know for a certainty that sometime today or tomorrow the girl and Gregory are going to meet in that apartment—or in one exactly like it."

"We're going to change it this time," I said. On my way out I stopped for a good look at Cronus. Nothing but a monster would give you a murderer, and a victim, and the place and approximate time, and make you completely helpless to do anything about it. I felt like giving Cronus a firm kick in a vital part of its anatomy.

I called off my dinner date with Stella and prowled around Manhattan looking for a big man with a pronounced limp. One speck of dust among the millions. I noticed with satisfaction that I was not alone in my search. Aircars were swooping in low for a quick look at pedestrians. Foot patrolmen were scrutinizing every passerby. And detectives would be making the rounds of the rooming houses and hotels with photographs. Cab and bus drivers would be alerted.

For a man who had no reason to hide, Michael Rolland Gregory was doing an expert job of keeping out of sight.

I radioed police headquarters at 10:00 P.M., and the Captain's voice exploded at me. "Where the hell have you been? The stakeout at the girl's apartment got Gregory. They're bringing him in."

I cut off without any of the formalities, and sprinted. I tore down the corridor to the D. F. C. room, and burst in on what might have been a funeral celebration. Walker sat with his face in his hands, and the Captain was pacing in a tight circle.

"He got away," the Captain snarled. "Snapped the handcuffs like toothpicks, beat up his escort and ran. The man must have the strength of a utility robot."

"How did they happen to pick him up?" I wanted to know.

"He came strolling down the street and started to go into the apartment building. Completely innocent about the whole thing, of course. He didn't have any idea we were looking for him."

"He has now," I said. "It's going to be great sport locating him again."

We had a small army loose in the area where Gregory escaped, but for all they found he might have burrowed into the pavement. I called Stella and asked her to stay home from work the next day. I got the stakeout on her aunt's apartment doubled.

I was up at dawn, prowling the streets, riding in patrolling aircars, and I suppose generally making a nuisance of myself with calls to headquarters. We put in a miserable day, and Gregory might have been hiding on Mars, for all the luck we had.

I had my evening meal at a little sandwich shop, and did a leisurely foot patrol along the street by Stella's apartment building. The stakeout was on the job, and the superintendent had Stella's lights on. I stood for a moment in the doorway, watching the few pedestrians, and then I signaled an aircab.

"I'd like to circle around here a bit," I said.

"Sure thing," the cabbie said.

We crisscrossed back and forth above the streets, and I squinted at pedestrians and watched the thin traffic pattern. Fifteen minutes later we were back by the apartment building.

"Circle low around the building," I said.

"Oh, no! Want me to lose my license? I can't go out of the air lanes."

"You can this time," I said. "Police."

He looked at my credentials, and grunted. "Why didn't you say so?"

There was a narrow strip of lawn behind the building, with a couple of trees, and then a dimly-lit alley. The cabbie handed me a pair of binoculars, and I strained my eyes on the sprawling shadows. I couldn't see anything suspicious, but I decided it might be worth a trip on foot.

The third time around I glanced at Stella's lighted windows—the rear ones—and gasped. A dark shadow clung to the side of the building, edging slowly along the ledge towards her window. Gregory.

"See that?" I said to the cabbie.

As we watched, he got the window open, and disappeared into the apartment.

I tried to radio the men on the stakeout, and couldn't rouse them. I called headquarters. Both Walker and Captain Marks were out. They would be back in a few minutes. But I didn't have minutes left.

"Skip it," I said. I snapped out a description of the situation, and cut off.

"Can you get close enough to get me through that window?" I asked the cabbie.

"I can try," he said. "But watch your step, fellow. It's a long drop."

He hovered close, and I grabbed the edge of the window and pulled myself through. Gregory faced me across the living room, a bewildered, panicky look on his huge, child-like face. I was thinking, how stupid can we get? From the way he came into Cronus's picture we should have known he didn't come through the door. Stella had come through the door, and we just assumed he was already in the room. But who would have thought Gregory could make like a human fly?

"All right, Gregory," I said. "You're under arrest."

Tears streaked his face. His jaw moved, but no sound came out. Suddenly I saw how we had blundered. This grotesquely oversized child meant no harm to anyone. Stella was the only person he'd ever known who treated him like a human being, and he wanted to see her again. For some reason he couldn't understand, the police were trying to prevent that. Suddenly the entire universe was against him, even Stella, and he was frightened.

And dangerous.

He lunged at me like a pile driver, and forced me back towards the open window. I got my gun out, and he just casually knocked it out of my hand. He had me on the window ledge, forcing me back and all I could see were the stars out in space.

Then the apartment door opened and closed and Gregory glanced back over his shoulder.

I screamed. "Run, Stella! Run—"

Then the night air was whistling past me. I bounced off an awning, crashed into the branches of a tree, struggled frantically for a hold, and fell through. From the window above came a piercing scream....

The Doctor had a face like an owl, and he bent over me, making funny clucking noises with his tongue. "There we are," he said, when he saw my eyes open. "Not bad at all."

"What's good about it?" I said.

"Young man, you fell six stories, and all you have is a broken leg and assorted bruises. You ask me what's good about it?"

"You wouldn't understand," I said. "Beat it." Stella's scream still rang in my ears. I twisted, and felt the heavy cast on my left leg. My mood merged and blended with the dull grey of the hospital room.

A nurse came tiptoing in, and smiled blandly when she saw I was awake. "You have some visitors," she said. "Do you want to see them?"

I knew it was the Captain. I hated to face him, but I said, "Let's get it over with."

The Captain loomed in the doorway, backed away, and came in again. And ahead of him walked Stella.

A different Stella—face pale and distorted, eyes registering shock and grief, but alive. But very much alive.

I started to get up, and the nurse placed a firm hand on each shoulder and held me to the bed. "Not so fast, sonny boy," she said.

Captain Marks moved up a chair for Stella. "Jim," she said. Her voice broke.

"I'll tell him," the Captain said. "It seems that Miss Emerson has a sister living in Boston. She didn't know anything about our problem, and she came down this evening for a visit. She had a key to Miss Emerson's apartment, and she walked in just at the right time to play a leading role in Cronus's drama."

"Was she—"

"No. Thankfully, no. Her condition is serious but she'll be all right again. The knife missed a vital spot by a fraction."

I relaxed. "What happened to Gregory?"

"He tried to go out the way he came in. There wasn't any tree to break his fall. And one other thing. I have an urgent message for you from Walker."

I glanced at the slip of paper. "Jim—for God's sake, stay out of aircars!"

"Cronus showed us your fall half an hour before it happened. From our angle, it looked as if you fell out of the aircab that was hovering over the building. Some time in the next twenty-four hours, Walker calculated, but we couldn't reach you."

"It wouldn't have made any difference," I said. "You know yourself...."

"Yes," he said. "I know."

His voice rambled on, while my eyes met Stella's. "So Cronus can show us the future," I heard him say, "but he can't change it, and neither can we."

"Cronus changed mine," I said, still looking at Stella.

The Captain took the hint, and left.

Five minutes later the phone rang, and I reached around Stella to answer it. It was Walker, and Stella held her face close to mine and listened.

"Just called to offer my congratulations," Walker said.

"Congratulations for what?"

"For your wedding. Cronus just spotted it."

I swore, but I kept it under my breath. "I haven't even asked the girl," I said, "and don't tell me I'm wearing that stupid arm band at my wedding, because I'm not."

"No, you're on crutches. But the Captain is standing up with you, and he's wearing his."

"All right," I said. "When is this glad event going to take place?"

"Four to eight days."

I slammed down the receiver, and kissed Stella's blushing face. "Cronus says we're getting married in four to eight days, and this is one time that monstrosity's going to be wrong. We'll get married tomorrow."

"All right, Jim, if you want to. But...."

"But what?"

"This is May twenty-eighth, and I want to be a June bride."

We were married five days later, and we went to Arizona on our honeymoon. I'd done some checking, and I knew Arizona was well outside of Cronus's range.