***

  BY FOUR THAT AFTERNOON MOOKHERJI had finished most of his chores. He had seen every patient; he had brought his progress charts up to date; he had fed a prognosis digest to the master computer that was the starport hospital’s control center; he had found time for a gulped lunch. Ordinarily, now, he could take the next four hours off, going back to his spartan room in the residents’ building at the edge of the starport complex for a nap, or dropping in at the recreation center to have a couple rounds of floater-tennis, or looking in at the latest cube-show, or whatever. His next round of patient-visiting didn’t begin until eight in the evening. But he couldn’t relax: there was that business of the quarantined spacemen to worry about. Nakadai had been sending test outputs over since two o’clock, and now they were stacked deep in Mookherji’s data terminal. Nothing had carried an urgent flag, so Mookherji had simply let the reports pile up; but now he felt he ought to have a look. He tapped the keys of the terminal, requesting printouts, and Nakadai’s outputs began to slide from the slot.

  Mookherji ruffled through the yellow sheets. Reflexes, synapse charge, degree of neural ionization, endocrine balances, visual response, respiratory and circulatory, cerebral molecular exchange, sensory percepts, EEG both enhanced and minimated . . . No, nothing unusual here. It was plain from the tests that the six men who had been to Norton’s Star were badly in need of a vacation—frayed nerves, blurred reflexes—but there was no indication of anything more serious than chronic loss of sleep. He couldn’t detect signs of brain lesions, infection, nerve damage, or other organic disabilities.

  Why the nightmares, then?

  He tapped out the phone number of Nakadai’s office. “Quarantine,” a crisp voice said almost at once, and moments later Nakadai’s lean, tawny face appeared on the screen. “Hello, Pete. I was just going to call you.”

  Mookherji said, “I didn’t finish up until a little while ago. But I’ve been through the outputs you sent over. Lee, there’s nothing here.”

  “As I thought.”

  “What about the men? You were supposed to call me if any of them went into nightmares.”

  “None of them have,” Nakadai said. “Falkirk and Rodriguez have been sleeping since eleven. Like lambs. Schmidt and Carroll were allowed to conk out at half past one. Webster and Schiavone hit the cots at three. All six are still snoring away, sleeping like they haven’t slept in years. I’ve got them loaded with equipment and everything’s reading perfectly normal. You want me to shunt the data to you?”

  “Why bother? If they aren’t hallucinating, what’ll I learn?”

  “Does that mean you plan to skip the mind-probes tonight?”

  “I don’t know,” Mookherji said, shrugging. “I suspect there’s no point in it, but let’s leave that part open. I’ll be finishing my evening rounds about eleven, and if there’s some reason to get into the heads of those spacemen then, I will.” He frowned. “But look—didn’t they say that each one of them went into the nightmares on every single sleep-shift?”

  “Right.”

  “And here they are, sleeping outside the ship to for the first time since the nightmares started, and none of them having any trouble at all. And no sign of possible hallucinogenic brain lesions. You know something, Lee? I’m starting to come around to a very silly hypothesis that those men proposed this morning.”

  “That the hallucinations were caused by some unseen alien being?” Nakadai asked.

  “Something like that. Lee, what’s the status of the ship they came in on?”

  “It’s been through all the routine purification checks, and now it’s sitting in an isolation vector until we have some idea of what’s on.”

  “Would I be able to get aboard it?” Mookherji asked.

  “I suppose so, yes, but—why—?”

  “On the wild shot that something external caused those nightmares and that that something may still be aboard the ship. And perhaps a lowlevel telepath like myself will be able to detect its presence. Can you set up clearance fast?”

  “Within ten minutes,” Nakadai said. “I’ll pick you up.”

  Nakadai came by shortly in a rollerbuggy. As they headed toward the landing field, he handed Mookherji a crumpled spacesuit and told him to put it on.

  “What for?”

  “You may want to breathe inside the ship. Right now it’s full of vacuum—we decided it wasn’t safe to leave it under atmosphere. Also it’s still loaded with radiation from the decontamination process. Okay?”

  Mookherji struggled into the suit.

  They reached the ship: a standard interstellar null-gravity-drive job, looking small and lonely in its corner of the field. A robot cordon kept it under isolation, but, tipped off by the control center, the robots let the two doctors pass. Nakadai remained outside; Mookherji crawled into the safety pouch and, after the hatch had gone through its admission cycle, entered the ship. He moved cautiously from cabin to cabin, like a man walking in a forest that was said to have a jaguar in every tree. While looking about, he brought himself as quickly as possible up to full telepathic receptivity, and, wide open, awaited telepathic contact with anything that might be lurking in the ship.

  —Go on. Do your worst.

  Complete silence on all mental wavelengths. Mookherji prowled everywhere: the cargo hold, the crew cabins, the drive compartments. Everything empty, everything still. Surely he would have been able to detect the presence of a telepathic creature in here, no matter how alien; if it was capable of reaching the mind of a sleeping spaceman, it should be able to reach the mind of a waking telepath as well. After fifteen minutes he left the ship, satisfied.

  “Nothing there,” he told Nakadai. “We’re still nowhere.”

  ***

  THE VSIIR WAS GROWING DESPERATE. It had been roaming this building all day; judging by the quality of the solar radiation coming through the windows, night was beginning to fall now. And, though there were open minds on every level of the structure, the Vsiir had had no luck in making contact. At least there had been no more terminations. But it was the same story here as on the ship: whenever the Vsiir touched a human mind, the reaction was so negative as to make communication impossible. And yet the Vsiir went on and on and on, to mind after mind, unable to believe that this whole planet did not hold a single human to whom it could tell its story. It hoped it was not doing severe damage to these minds it was approaching; but it had its own fate to consider.

  Perhaps this mind would be the one. The Vsiir started once more to tell its tale—

  ***

  HALF PAST NINE AT NIGHT. Dr. Peter Mookherji, bloodshot, tense, hauled himself through his neuropathological responsibilities. The ward was full: a schizoid collapse, a catatonic freeze, Satina in her coma, half a dozen routine hysterias, a couple of paralysis cases, an aphasic, and plenty more, enough to keep him going for sixteen hours a day and strain his telepathic powers, not to mention his conventional medical skills, to their limits. Some day the ordeal of residency would be over; some day he’d be quit of this hospital, and would set up private practice on some sweet tropical isle, and commute to Bombay on weekends to see his family, and spend his holidays on planets of distant stars, like any prosperous medical specialist . . . Some day. He tried to banish such lavish fantasies from his mind. If you’re going to look forward to anything, he told himself, look forward to midnight. To sleep. Beautiful, beautiful sleep. And in the morning it all begins again, Satina and the coma, the schizoid, the catatonic, the aphasic . . .

  As he stepped into the hall, going from patient to patient, his annunciator said, “Dr. Mookherji, please report at once to Dr. Bailey’s office.”

  Bailey? The head of the neuropathology department, still hitting the desk this late. What now? But of course there was no ignoring such a summons. Mookherji notified the control center that he had been called off his rounds, and made his way quickly down the corridor to the frosted-glass door marked SAMUEL F. BAILEY, M.D.

  He found at least half the neuropath staff there already: four of the other senior residents, most of the interns, even a few of the high-level doctors. Bailey, a puffy-faced, sandy-haired, fiftyish man of formidable professional standing, was thumbing a sheaf of outputs and scowling. He gave Mookherji a faint nod by way of greeting. They were not on the best of terms; Bailey, somewhat old-school in his attitudes, had not made a good adjustment to the advent of telepathy as a tool in the treatment of mental disturbance. “As I was just saying,” Bailey began, “these reports have been accumulating all day, and they’ve all been dumped on me, God knows why. Listen: two cardiac patients under sedation undergo sudden violent shocks, described by one doctor as sensory overloads. One reacts with cardiac arrest, the other with cerebral hemorrhage. Both die. A patient being treated for endocrine restabilization develops a runaway adrenaline flow while asleep, and gets a six-month setback. A patient undergoing brain surgery starts lurching around on the operating table, despite adequate anesthesia, and gets badly carved up by the lasers. Et cetera. Serious problems like this all over the hospital today. Computer check of general EEG patterns shows that fourteen patients, other than those mentioned, have experienced exceptionally severe episodes of nightmare in the last eleven hours, nearly all of them of such impact that the patient has sustained some degree of psychic damage and often actual physiological harm. Control center reports no case histories of previous epidemics of bad dreams. No reason to suspect a widespread dietary imbalance or similar cause for the outbreak. Nevertheless, sleeping patients are continuing to suffer, and those whose condition is particularly critical may be exposed to grave risks. Effective immediately, sedation of critical patients has been interrupted where feasible, and sleep schedules of other patients have been rearranged, but this is obviously not an expedient that is going to do much good if this outbreak continues into tomorrow.”

  Bailey paused, glanced around the room, let his gaze rest on Mookherji. “Control center has offered one hypothesis: that a psychopathic individual with strong telepathic powers is at large in the hospital, preying on sleeping patients and transmitting images to them that take the form of horrifying nightmares. Mookherji, what do you make of that idea?”

  Mookherji said, “It’s perfectly feasible, I suppose, although I can’t imagine why any telepath would want to go around distributing nightmares. But has control center correlated any of this with the business over at the quarantine building?”

  Bailey stared at his output slips. “What business is that?”

  “Six spacemen who came in early this morning, reporting that they’d all suffered chronic nightmares on their voyage homeward. Dr. Lee Nakadai’s been testing them; he called me in as a consultant, but I couldn’t discover anything useful. I imagine there are some late reports from Nakadai in my office, but—”

  Bailey said, “Control center seems only to be concerned about events in the hospital, not in the starport complex as a whole. And if your six spacemen had their nightmares during their voyage, there’s no chance that their symptoms are going to find their way onto—”

  “That’s just it!” Mookherji cut in. “They had their nightmares in space. But they’ve been asleep since morning, and Nakadai says they’re resting peacefully. Meanwhile an outbreak of hallucinations has started over here. Which means that whatever was bothering them during their voyage has somehow got loose in the hospital today—some sort of entity capable of stirring up such ghastly dreams that they bring veteran spacemen to the edge of nervous breakdowns and can seriously injure or even kill someone in poor health.” He realized that Bailey was looking at him strangely, and that Bailey was not the only one. In a more restrained tone, Mookherji said, “I’m sorry if this sounds fantastic to you. I’ve been checking it out all day, so I’ve had some time to get used to the concept. And things began to fit together for me just now. I’m not saying that my idea is necessarily correct. I’m simply saying that it’s a reasonable notion, that it links up with the spacemen’s own idea of what was bothering them, that it corresponds to the shape of the situation—and that it deserves a decent investigation, if we’re going to stop this before we lose some more patients.”

  “All right, doctor,” Bailey said. “How do you propose to conduct the investigation?”

  Mookherji was shaken by that. He had been on the go all day; he was ready to fold. Here was Bailey abruptly putting him in charge of this snark-hunt, without even asking! But he saw there was no way to refuse. He was the only telepath on the staff. And, if the supposed creature really was at large in the hospital, how could be tracked except by a telepath?

  Fighting back his fatigue, Mookherji said rigidly, “Well, I’d want a chart of all the nightmare cases, to begin with, a chart showing the location of each victim and the approximate time of onset hallucination—”

  ***

  THEY WOULD BE PREPARING FOR the Festival of Changing, now, the grand climax of the winter. Thousands of Vsiirs in the metamorphic phase would be on their way toward the Valley of Sand, toward that great natural amphitheater where the holiest rituals were performed. By now the firstcomers would already have taken up their positions, facing the west, waiting for the sunrise. Gradually the rows would fill as Vsiirs came in from every part of the planet, until the golden valley was thick with them, Vsiirs that constantly shifted their energy levels, dimensional extensions, and inner resonances, shuttling gloriously through the final joyous moments of the season of metamorphosis, competing with one another in a gentle way to display the great variety of form, the most dynamic cycle of physical changes—and, when the first red rays of the sun crept past the Needle, the celebrants would grow even more frenzied, dancing and leaping and transforming themselves with total abandon, purging themselves of the winter’s flam boyance as the season of stability swept across the world. And finally, in the full blaze of sunlight, they would turn to one another in renewed kinship, embracing, and—

  The Vsiir tried not to think about it. But it was hard to repress that sense of loss, that pang of nostalgia. The pain grew more intense with every moment. No imaginable miracle would get the Vsiir home in time for the Festival of Changing, it knew, and yet it could not really believe that such a calamity had befallen it.

  Trying to touch minds with humans was useless. Perhaps if it assumed a form visible to them, and let itself be noticed, and then tried to open verbal communication—

  But the Vsiir was so small, and these humans were so large. The dangers were great. The Vsiir, clinging to a wall and carefully keeping its wavelength well beyond the ultraviolet, weighed one risk against another, and, for the moment, did nothing.

  ***

  “ALL RIGHT,” MOOKHERJI SAID FOGGILY, a little before midnight. “I think we’ve got the trail clear now.” He sat before a wall-sized screen on which the control center had thrown a three-dimensional schematic plan of the hospital. Bright red dots marked the place of each nightmare incident, yellow dashes the probable path of the unseen alien creature. “It came in the side way, probably, straight off the ship, and went into the cardiac wing first. Mrs. Maldonado’s bed here, Mr. Guinness’ over here, eh? Then it went up to the second level, coming around to the front wing and impinging on the minds of patients here and here and here between ten and eleven in the morning. There were no reported episodes of hallucination in the next hour and ten minutes, but then came that nasty business in the third-level surgical gallery, and after that—” Mookherji’s aching eyes closed a moment; it seemed to him that he could still see the red dots and yellow dashes. He forced himself to go on, tracing the rest of the intruder’s route for his audience of doctors and hospital security personnel. At last he said, “That’s it. I figure that the thing must be somewhere between the fifth and eighth levels by now. It’s moving much more slowly than it did this morning, possibly running out of energy. What we have to do is keep the hospital’s wings tightly sealed to prevent its free movement, if that can be done, and attempt to narrow down the number of places whom it might be found.”

  One of the security men said, a little belligerently, “Doctor, just how are we supposed to find an invisible entity?”

  Mookherji struggled to keep impatience out of his voice. “The visible spectrum isn’t the only sort of electromagnetic energy in the universe. If this thing is alive, it’s got to be radiating somewhere along the line. You’ve got a master computer with a million sensory pickups mounted all over the hospital. Can’t you have the sensors scan for a point-source of infrared or ultraviolet moving through a room? Or even X-rays, for God’s sake: we don’t know where the radiation’s likely to be. Maybe it’s a gamma emitter, even. Look, something wild is loose in this building, and we can’t see it, but the computer can. Make it search.”

  Dr. Bailey said, “Perhaps the energy we ought to be trying to trace it by is, ah, telepathic energy, doctor.”

  Mookherji shrugged. “As far as anybody knows, telepathic impulses propagate somewhere outside the electromagnetic spectrum. But of course you’re right that I might be able to pick up some kind of output, and I intend to make a floor-by-floor search as soon as this briefing session is over.” He turned toward Nakadai. “Lee, what’s the word from your quarantined spacemen?”

  “All six went through eight-hour sleep periods today without any sign of a nightmare episode: there was some dreaming, but all of it normal. In the past couple of hours I’ve had them on the phone talking with some of the patients who had the nightmares, and everybody agrees that the kind of dreams people have been having here today are the same in tone, texture, and general level of horror as the ones the men had aboard the ship. Images of bodily destruction and alien landscapes, accompanied by an overwhelming, almost intolerable, feeling of isolation, loneliness, separation from one’s own kind.”

  “Which would fit the hypothesis of an alien being as the cause,” said Martinson of the psychology staff. “If it’s wandering around trying to communicate with us, trying to tell us it doesn’t want to be here, say, and its communications reach human minds only in the form of frightful nightmares—”