I followed a long, empty corridor, then forked right. I had never lived on the Station, but duringmy training on Earth I had spent six weeks in an exact replica of it; when I reached a shortaluminum stairway, I knew where it led.

The library was in darkness, and I had to fumble for the light switch. I first consulted the index,then dialled the coordinates for the first volume of the Solarist Annual and its supplement. Ared light came on. I turned to the register: the two books were marked out to Gibarian, togetherwith The Little Apocrypha. I switched the lights off and returned to the lower deck.

In spite of having heard the footsteps receding, I was afraid to re-enter Gibarian's room. Shemight return. I hesitated for some time outside the door; finally, pressing down the handle, Iforced myself to go in.

There was no one in the room. I began rummaging through the books scattered beneath thewindow, interrupting my search only to close the locker door: I could not bear the sight of theempty space among the work-suits.

The supplement was not in the first pile, so, one by one, I started methodically picking up therest of the books around the room. When I reached the final pile, between the bed and thewardrobe, I found the volume I was looking for.

I was hoping to find some sort of clue and, sure enough, a book-marker had been slippedbetween the pages of the index. A name, unfamiliar to me, had been underlined in red: AndréBerton. The corresponding page numbers indicated two different chapters; glancing at the first,I learnt that Berton was a reserve pilot on Shannahan's ship. The second reference appearedabout a hundred pages further on.

At first, it seemed, Shannahan's expedition had proceeded with extreme caution. When,however, after sixteen days, the plasmatic ocean had not only shown no signs of aggression,but appeared to shun any direct contact with men and machines, recoiling whenever anythingapproached its surface, Shannahan and his deputy, Timolis, discontinued some of theprecautions which were hindering the progress of their work. The force fences which had beenused to demarcate and protect the working areas were taken back to base, and the expeditionsplit up into groups of two or three men, some groups making reconnaissance flights over aradius of some several hundred miles.

Apart from some unexpected damage to the oxygen-supply systems—the atmosphere had anunusually corrosive effect on the valves, which had to be replaced almost daily—four dayspassed without mishap. On the morning of the fifth day—21 days after the arrival of theexpedition—two scientists, Carucci and Fechner (the first a radiobiologist, the second aphysicist), left on a mission aboard a hovercraft. Six hours later, the explorers were overdue.

Timolis, who was in charge of the base in Shannahan's absence, raised the alarm and divertedevery available man into search-parties.

By a fatal combination of circumstances, long-range radio contact had been cut that morningan hour after the departure of the exploration groups—a large spot had appeared on the red sun,producing a heavy bombardment of charged particles in the upper atmosphere. Only the ultra-shortwave transmitters continued to function, and contact was restricted to a radius of abouttwenty miles. As a crowning stroke of bad luck, a thick fog descended just before sunset andthe search had to be called off.

The rescue teams were returning to base when the hovercraft was spotted by a flitter, barely 24miles from the command-ship. The engine was running and the machine, at first sightundamaged, was hovering above the waves. Carucci alone could be seen, semi-conscious, inthe glass-domed cockpit.

The hovercraft was escorted back to base. After treatment, Carucci quickly regainedconsciousness, but could throw no light on Fechner's disappearance. Just after they had decidedto return to base a valve in his oxygen-gear had failed and a small amount of unfiltered gas hadpenetrated his atmosphere-suit. In an attempt to repair the valve, Fechner had been forced toundo his safety belt and stand up. That was the last thing Carucci could remember.

According to the experts who reconstructed the sequence of events, Fechner must have openedthe cabin roof because it impeded his movements—a perfectly legitimate thing to do since thecabins of these vehicles were not air-tight, the glass dome merely providing some protectionagainst infiltration and turbulence. While Fechner was occupied with his colleague, his ownoxygen supply had probably been damaged and, no longer realizing what he was doing, he hadpulled himself up on to the superstructure, from which he had fallen into the ocean.

Fechner thus became the ocean's first victim. Although the atmosphere-suit was buoyant, theysearched for his body without success. It was, of course, possible that it was still floatingsomewhere on the surface, but the expedition was not equipped for a thorough search of thisimmense, undulating desert, covered with patches of dense fog.

By dusk, all but one of the search craft had returned to base; only a big supply helicopterpiloted by André Berton was still missing. Just as they were about to raise the alarm, theaircraft appeared. Berton was obviously suffering from nervous shock; after struggling out ofhis suit, he ran round in circles like a madman. He had to be overpowered, but went onshouting and sobbing. It was rather surprising behavior to put it mildly, on the part of a manwho had been flying for seventeen years and was well used to the hazards of cosmicnavigation. The doctors assumed that he too was suffering from the effects of unfiltered gases.

Having more or less recovered his senses, Berton nevertheless refused to leave the base, oreven to go near the window overlooking the ocean. Two days later, he asked for permission todictate a flight-report, stressing the importance of what he was about to reveal. This report wasstudied by the expeditionary council, who concluded that it was the morbid creation of a mindunder the influence of poisonous gases from the atmosphere. As for the supposed revelations,they were evidently regarded as part of Berton's clinical history rather than that of theexpedition itself, and they were not described.

So much for the supplement. It seemed to me that Berton's report must at any rate provide akey to the mystery. What strange happening could have had such a shattering effect on aveteran space-pilot? I began to search through the books once more, butThe Little Apocrypha was not to be found. I was growing more and more exhausted and left theroom, having decided to postpone the search until the following day.

As I was passing the foot of the stairway, I noticed that the aluminum treads were streakedwith light falling from above. Sartorius was still at work. I decided to go up and see him.

It was hotter on the upper deck, but the paper strips still fluttered frenziedly at the air-vents.

The corridor was wide and low-ceilinged. The main laboratory was enclosed by a thick panelof opaque glass in a chrome embrasure. A dark curtain screened the door on the inside, and thelight was coming from windows let in above the lintel. I pressed down the handle, but, as Iexpected, the door refused to budge. The only sound from the laboratory was an intermittentwhine like that of a defective gas jet. I knocked. No reply. I called:

"Sartorius! Dr. Sartorius! I'm the new man, Kelvin. I must see you, it's very important. Pleaselet me in!"There was a rustling of papers.

"It's me, Kelvin. You must have heard of me. I arrived off the Prometheus a few hours ago."I was shouting, my lips glued to the angle where the door joined the metal frame.

"Dr. Sartorius, I'm alone. Please open the door!"Not a word. Then the same rustling as before, followed by the clink of metal instruments on atray. Then…I could scarcely believe my ears…there came a succession of little short footsteps,like the rapid drumming of a pair of tiny feet, or remarkably agile fingers tapping out therhythm of steps on the lid of an empty tin box.

I yelled:

"Dr. Sartorius, are you going to open this door, yes or no?"No answer. Nothing but the pattering, and, simultaneously, the sound of a man walking ontiptoe. But, if the man was moving about, he could not at the same time be tapping out animitation of a child's footsteps.

No longer able to control my growing fury, I burst out:

"Dr. Sartorius, I have not made a sixteen-month journey just to come here and play games! I'llcount up to ten. If you don't let me in, I shall break down the door!"In fact, I was doubtful whether it would be easy to force this particular door, and the dischargeof a gas pistol is not very powerful. Nevertheless, I was determined somehow or other to carryout my threat, even if it meant resorting to explosives, which I could probably find in themunition store. I could not draw back now; I could not go on playing an insane game with allthe cards stacked against me.

There was the sound of a struggle—or was it simply objects being thrust aside? The curtainwas pulled back, and an elongated shadow was projected on to the glass.

A hoarse, high-pitched voice spoke:

"If I open the door, you must give me your word not to come in.""In that case, why open it?""I'll come out.""Very well, I promise."The silhouette vanished and the curtain was carefully replaced.

Obscure noises came from inside the laboratory. I heard a scraping—a table being draggedacross the floor? At last, the lock clicked back, and the glass panel opened just enough to allowSartorius to slip through into the corridor.

He stood with his back against the door, very tall and thin, all bones under his white sweater.

He had a black scarf knotted around his neck, and over his arm he was carrying a laboratorysmock, covered with chemical burns. His head, which was unusually narrow, was cocked toone side. I could not see his eyes: he wore curved dark glasses, which covered up half his face.

His lower jaw was elongated; he had bluish lips and enormous, blue-tinged ears. He wasunshaven. Red anti-radiation gloves hung by their laces from his wrists.

For a moment we looked at one another with undisguised aversion. His shaggy hair (he hadobviously cut it himself) was the color of lead, his beard grizzled. Like Snow, his forehead wasburnt, but the lower half only; above it was pallid. He must have worn some kind of cap whenexposed to the sun.

"Well, I'm listening," he said.

I had the impression that he did not care what I had to say to him. Standing there, tense, stillpressed against the door panel, his attention was mainly directed to what was going on behindhim.

Disconcerted, I hardly knew how to begin.

"My name is Kelvin," I said, "You must have heard about me. I am, or rather I was, a colleagueof Gibarian's."His thin face, entirely composed of vertical planes, exactly as I had always imagined DonQuixote's, was quite expressionless. This blank mask did not help me to find the right words.

"I heard that Gibarian was dead…" I broke off.

"Yes. Go on, I'm listening." His voice betrayed his impatience.

"Did he commit suicide? Who found the body, you or Snow?""Why ask me? Didn't Dr. Snow tell you what happened?""I wanted to hear your own account.""You've studied psychology, haven't you, Dr. Kelvin?""Yes. What of it?""You think of yourself as a servant of science?""Yes, of course. What has that to do with…""You are not an officer of the law. At this hour of the day, you should be at work, but insteadof doing the job you were sent here for, you not only threaten to force the door of mylaboratory, you question me as though I were a criminal suspect."His forehead was dripping with sweat. I controlled myself with an effort. I was determined toget through to him. I gritted my teeth and said:

"You are suspect, Dr. Sartorius. What is more, you're well aware of it!""Kelvin, unless you either retract or apologize, I shall lodge a complaint against you.""Why should I apologize? You're the one who barricaded himself in this laboratory instead ofcoming out to meet me, instead of telling me the truth about what is going on here. Have yougone completely mad? What are you—a scientist, or a miserable coward?"I don't know what other insults I hurled at him. He did not even flinch. Globules of sweattrickled down over the enlarged pores of his cheeks. Suddenly I realized that he had not heard aword I was saying. Both hands behind his back, he was holding the door in position with all hisstrength; it was rattling as though someone inside were firing bursts from a machine-gun at thepanel.

In a strange, high-pitched voice, he moaned:

"Go away. For God's sake, leave me. Go downstairs, I'll join you later. I'll do whatever youwant, only please go away now."His voice betrayed such exhaustion that instinctively I put out my arms to help him control thedoor. At this, he uttered a cry of horror, as though I had pointed a knife at him. As I retreated,he was shouting in his falsetto voice: "Go away! Go away! I'm coming, I'm coming, I'mcoming! No! No!" He opened the door and shot inside. I thought I saw a shining yellow discflash across his chest.

Now a muffled clamor rose from the laboratory; a huge shadow appeared, as the curtain wasbrushed momentarily aside; then it fell back into place and I could see nothing more. What washappening inside that room? I heard running footsteps, as though a mad chase were in progress,followed by a terrifying crash of broken glass and the sound of a child's laugh.

My legs were trembling, and I stared at the door, appalled. The din had subsided, giving way toan uneasy silence. I sat down on a window ledge, too stunned to move; my head was splitting.

From where I was, I could see only a part of the corridor encircling the laboratory. I was at thesummit of the Station, beneath the actual shell of the superstructure; the walls were concaveand sloping, with oblong windows a few yards apart. The blue day was ending, and, as theshutters grated upwards, a blinding light shone through the thick glass. Every metal fitting,every latch and joint, blazed, and the great glass panel of the laboratory door glittered with palecoruscations. My hands looked grey in the spectral light. I noticed that I was holding the gaspistol; I had not realized that I had taken it out of its holster, and replaced it. What use could Ihave made of it—or even of a gamma pistol, had I had one? I could hardly have taken thelaboratory by force.

I got up. The disc of the sun, reminiscent of a hydrogen explosion, was sinking into the ocean,and as I descended the stairway I was pierced by a jet of horizontal rays which was almosttangible. Halfway downstairs I paused to think, then went back up the steps and followed thecorridor round the laboratory. Soon, I came across a second glass door, exactly like the first; Imade no attempt to open it, knowing that it would be locked.

I was looking for an opening or vent of some sort. The idea of spying on Sartorius had come tome quite naturally, without the least sense of shame. I was determined to have done withconjecture and discover the truth, even if, as I imagined it would, the truth provedincomprehensible. It struck me that the laboratory must be lit from above by windows let intothe dome. It should be possible, therefore, to spy on Sartorius from the outside. But first Ishould have to equip myself with an atmosphere-suit and oxygen gear.

When I reached the deck below, I found the door of the radio-cabin ajar. Snow, sunk in hisarmchair, was asleep. At the sound of my footsteps, he opened his eyes with a start.

"Hello, Kelvin!" he croaked. "Well, did you discover anything?""Yes…he's not alone." Snow grinned sourly.

"Oh, really? Well, that's something. Has he got visitors?""I can't understand why you won't tell me what's going on," I retorted impulsively. "Since Ihave to remain here, I'm bound to find out the truth sooner or later. Why the mystery?""When you've received some visitors yourself, you'll understand."I had the impression that my presence annoyed him and he had no desire to prolong theconversation. I turned to go. "Where are you off to?" I did not answer.

The hangar-deck was just as I had left it. My burnt-out capsule still stood there, gaping open,on its platform. On my way to select an atmosphere-suit, I suddenly realized that the skylightsthrough which I hoped to observe Sartorius would probably be made of slabs of opaque glass,and I lost interest in my venture on to the outer hull.

Instead, I descended the spiral stairway which led to the lower-deck store rooms. The crampedpassage at the bottom contained the usual litter of crates and cylinders.

The walls were sheeted in bare metal which had a bluish glint. A little further on, the frostedpipes of the refrigeration plant appeared beneath a vault and I followed them to the far end ofthe corridor where they vanished into a cooling-jacket with a wide, plastic collar. The door tothe cold store was two inches thick and lagged with an insulating compound. When I opened it,the icy cold gripped me. I stood, shivering, on the threshold of a cave carved out of an iceberg;the huge coils, like sculptured reliefs, were hung with stalactites. Here, too, buried beneath acovering of snow, there were crates and cylinders, and shelves laden with boxes andtransparent bags containing a yellow, oily substance. The vault sloped downwards to where acurtain of ice hid the back of the cave. I broke through it. An elongated figure, covered with asheet of canvas, lay stretched out on an aluminum rack.

I lifted a corner of the canvas and recognised the stiff features of Gibarian. His glossy blackhair clung tightly to his skull. The sinews of his throat stood out like bones. His glazed eyesstared up at the vault, a tear of opaque ice hanging from the corner of each lid. The cold was sointense that I had to clench my teeth to prevent them from chattering. I touched Gibarian'scheek; it was like touching a block of petrified wood, bristling with black prickly hairs. Thecurve of the lips seemed to express an infinite, disdainful patience.

As I let the canvas fall, I noticed, peeping out from beneath the folds at the foot, five round,shiny objects, like black pearls, ranged in order of size. I stiffened with horror.

What I had seen were the round pads of five bare toes. Under the shroud, flattened againstGibarian's body, lay the Negress. Slowly, I pulled back the canvas. Her head, covered in frizzyhair twisted up into little tufts, was resting in the hollow of one massive arm. Her backglistened, the skin stretched taut over the spinal column. The huge body gave no sign of life. Ilooked again at the soles of her naked feet; they had not been flattened or deformed in any wayby the weight which they had had to carry. Walking had not calloused the skin, which was asunblemished as that of her shoulders.

With a far greater effort than it had taken to touch Gibarian's corpse, I forced myself to touchone of the bare feet. Then I made a second bewildering discovery: this body, abandoned in adeep freeze, this apparent corpse, lived and moved. The woman had withdrawn her foot, like asleeping dog when you try to take its paw.

"She'll freeze," I thought confusedly, but her flesh had been warm to the touch, and I evenimagined I had felt the regular beating of her pulse. I backed out and fled.

As I emerged from the white cave, the heat seemed suffocating. I climbed the spiral stairwayback to the hangar-deck.

I sat on the hoops of a rolled-up parachute and put my head in my hands. I was stunned. Mythoughts ran wild. What was happening to me? If my reason was giving way, the sooner I lostconsciousness the better. The idea of sudden extinction aroused an inexpressible, unrealistichope.

Useless to go and find Snow or Sartorius: no one could fully understand what I had justexperienced, what I had seen, what I had touched with my own hands. There was only onepossible explanation, one possible conclusion: madness. Yes, that was it, I had gone mad assoon as I arrived here. Emanations from the ocean had attacked my brain, and hallucinationhad followed hallucination. Rather than exhaust myself trying to solve these illusory riddles, Iwould do better to ask for medical assistance, to radio the Prometheus or some other vessel, tosend out an SOS.

Then a curious change came over me: at the thought that I had gone mad, I calmed down.

And yet…I had heard Snow's words quite clearly. If, that is, Snow existed and I had everspoken to him. The hallucinations might have begun much earlier. Perhaps I was still on boardthe Prometheus, perhaps I had been stricken with a sudden mental illness and was nowconfronting the creations of my own inflamed brain.

Assuming that I was ill, there was reason to believe that I would get better, which gave mesome hope of deliverance—a hope irreconcilable with a belief in the reality of the tanglednightmares through which I had just lived.

If only I could think up some experiment in logic—a key experiment—which would revealwhether I had really gone mad and was a helpless prey to the figments of my imagination, orwhether, in spite of their ludicrous improbability, I had been experiencing real events.

As I turned all this over in my mind, I was looking at the monorail which led to the launchingpad. It was a steel girder, painted pale green, a yard above the ground. Here and there, the paintwas chipped, worn by the friction of the rocket trolleys. I touched the steel, feeling it growwarm beneath my fingers, and rapped the metal plating with my knuckles. Could madnessattain such a degree of reality? Yes, I answered myself. After all, it was my own subject, Iknew what I was talking about.

But was it possible to work out a controlled experiment? At first I told myself that it was not,since my sick brain (if it really was sick) would create the illusions I demanded of it. Evenwhile dreaming, when we are in perfectly good health, we talk to strangers, put questions tothem and hear their replies. Moreover, although our interlocutors are in fact the creations of ourown psychic activity, evolved by a pseudo-independent process, until they have spoken to uswe do not know what words will emerge from their lips. And yet these words have beenformulated by a separate part of our own minds; we should therefore be aware of them at thevery moment that we think them up in order to put them into the mouths of imaginary beings.

Consequently, whatever form my proposed test were to take, and whatever method I used toput it into execution, there was always the possibility that I was behaving exactly as in a dream.

Neither Snow nor Sartorius having any real existence, it would be pointless to put questions tothem.

I thought of taking some powerful drug, peyotl for example, or another preparation inducingvivid hallucinations. If visions ensued, this would prove that I had really experienced theserecent events and that they were part and parcel of the surrounding material reality. But then,no, I thought, this would not constitute the proof I needed, since I knew the effects of the drug(which I should have chosen for myself) and my imagination could suggest to me the doubleillusion of having taken the drug and of experiencing its effects.

I was going around in circles; there seemed to be no escape. It was not possible to think exceptwith one's brain, no one could stand outside himself in order to check the functioning of hisinner processes. Suddenly an idea struck me, as simple as it was effective.

I leapt to my feet and ran to the radio-cabin. The room was deserted. I glanced at the electricclock on the wall. Nearly four o'clock, the fourth hour of the Station's artificial night-time.

Outside, the red sun was shining. I quickly plugged in the long-range transmitter, and while thevalves warmed up, I went over in my mind the principal stages of the experiment.

I could not remember the call-sign for the automatic station on the satellite, but I found it on acard hanging above the main instrument panel, sent it out in Morse, and received the answeringsignal eight seconds later. The satellite, or rather its electronic brain, identified itself by arhythmic pulse.

I instructed the satellite to give me the figures of the galactic meridians it was traversing at 22secondintervals while orbiting Solaris, and I specified an answer to five decimal points.

Then I sat and waited for the reply. Ten minutes later, it arrived. I tore off the strip of freshlyprinted paper and hid it in a drawer, taking care not to look at it. I went to the bookcase andtook out the big galactic charts, the logarithm tables, a calendar giving the daily path of thesatellite, and various other textbooks. Then I sat down to work out for myself the answer to thequestion I had posed.

For an hour or more, I integrated the equations. It was a long time since I had tackled suchelaborate calculations. My last major effort in this direction must have been my practicalastronomy exam.

I worked at the problem with the help of the Station's giant computer. My reasoning went asfollows: by making my calculations from the galactic charts, I would obtain an approximatecross-check with the results provided by the satellite. Approximate because the path of thesatellite was subject to very complex variations due to the effects of the gravitational forces ofSolaris and its two suns, as well as to the local variations in gravity caused by the ocean. WhenI had the two series of figures, one furnished by the satellite and the other calculatedtheoretically on the basis of the galactic charts, I would make the necessary adjustments andthe two groups would then coincide up to the fourth decimal point, discrepancies due to theunforeseeable influence of the ocean arising only at the fifth.

If the figures obtained from the satellite were simply the product of my deranged mind, theycould not possibly coincide with the second series. My brain might be unhinged, but it couldnot conceivably compete with the Station's giant computer and secretly perform calculationsrequiring several months' work. Therefore if the figures corresponded, it would follow that theStation's computer really existed, that I had really used it, and that I was not delirious.

My hands trembled as I took the telegraphic tape out of the drawer and laid it alongside thewide band of paper from the computer. As I had predicted, the two series of numberscorresponded up to the fourth decimal point.

I put all the papers away in the drawer. So the computer existed independently of me; thatmeant that the Station and its inhabitants really existed too.

As I was closing the drawer, I noticed that it was stuffed with sheets of paper covered withhastily scribbled sums. A single glance told me that someone had already attempted anexperiment similar to mine and had asked the satellite, not for information about the galacticmeridians, but for the measurements of Solaris's albedo at intervals of forty seconds.

I was not mad. The last ray of hope was extinguished. I unplugged the transmitter, drank theremains of the soup in the vacuum flask, and went to bed.