Pain flared, and in a moment a red spot appeared where his fingernail had dug into the skin.

Mach had to lean against a tree to keep from reeling. He was alive! His body was fashioned of flesh; it had a heart, and it felt direct pain.

Now he knew that he had suffered a far greater breakthrough than he had antic.i.p.ated. He had made his belief in the impossible total, and stepped into the realm of the living. Of course this could not be literal, but even as a dream it was astonishing, for robots did not dream. That new circuit had really performed! He had achieved what no robot had ever done before: fashioned a total illusion of life.

But now that he had done this, what had he really accomplished? Metallic insanity? Was his body lying on the bed while his brain was locked into its own program of fantasy? That could be fun for a while, but after a few hours he would be in trouble, because his mother would discover him and bring in a technician to repair the glitch. If the case were judged to be too extreme, they would reprogram his brain unit, wiping out everything he had accomplished here, including the memory of it. He would be forever after bound to his natural robotic state.

That, he realized, would be disaster. He was delighted to have achieved this breakthrough. To generate even the facsimile of life, even within his dream-in fact, the mere fact of the dream was extraordinary. He had to preserve and improve this ability-which meant he had to master the technique of releasing himself from it. It would be best if no one else know of this accomplishment, until he had perfected it.

He concentrated, trying to release the dream. Nothing happened. He remained in the glade, his heart still beating, his breath still breathing.

He didn't know how to turn off the dream. But perhaps he wasn't helpless. His dream had to have limits; if he explored beyond those limits, he might force it to abort.

He started down the path. He didn't care where it went; he just meant to follow it beyond the definition that it had. To force the issue.

The path wound through the forest, following a contour. Parts of it were rocky, and he discovered that his feet were tender. Since he had gone barefoot for ail his existence, and his soles had been of toughened pseudoflesh, this was a surprise. But it was consistent with the illusion of living flesh, especially if it was supposed to have used boots.

He came to a fork in the path. Which way should he go? One path led downward, the other upward. He felt thirsty, which was another aspect of the verisimilitude of this dream, so he took the one leading down. There might be a river there.

There was indeed a stream. The water wended lazily through a swampy region. The path descended into this and disappeared. Mach considered, then got down flat and put his lips to the closest clear water he spied. He sucked, employing the physics that he had described to Agape.

Agape? How far away the alien female seemed now!

There was a sudden snort behind him. He jerked his head up, twisting about to look back. It was a man- with the head of a pig. The snout was flattened in the porcine manner, and cruel tusks glinted at the sides of the mouth.

Mach scrambled up. The pighead stepped aggressively forward. Somehow it reminded him of Ware, the android.

"Now look, creature," Mach said nervously. "I don't want to bother you. I just want to drink." For the mouthful he had taken in wasn't enough.

"Zdringk!" the pighead snorted. "Owrs!"

He was claiming this drinking-spot? "Then I'll drink farther along," Mach said, trying to edge around the creature.

"Zrriverr owrs!" the pighead proclaimed.

"The whole river is yours? But that's unreasonable!"

The pighead lowered his head and ground his tusks together. It seemed that he was not about to be reasonable. He reminded Mach even more strongly of the android.

Mach considered again. He was thirsty, and this seemed to be the only reasonable source of water. If he gave this up, he wasn't sure where or when he would find another drinking place. He would have to stand his ground.

"I feel that I have about as much right to drink as you do," he said. "Please allow me to-"

The pighead squealed with rage. Immediately there was a rustling in the vicinity, and the sound of feet striking the ground. Several other pigmen appeared- and several pigwomen too. All were naked and completely humanoid, the females quite attractively so, except for the heads. All looked menacing.

The pigheads blocked off the path. Mach had to retreat into the water. He discovered that the path continued under the surface, firm though slippery; he could proceed without getting dunked, as it was only knee-deep.

The pigheads followed him a little way, but then halted, snorting angrily. Mach went on-and abruptly stepped off the edge and landed up to his waist in water-covered muck. He should have watched where he was going!

There was a hiss. He looked-and spied a man swimming toward him. Relieved, but cautious, he scrambled back to the firm path, and stood knee-deep as the man came close.

And the man turned out to be only the head of a man. The body was that of a monstrous python, undulating through the water.

Mach had thought this was a dream. But he had never heard or read of either pigmen or snakemen, and his computer-type brain was not strong on creative imagination. If he had tried to populate this dream, he would have done it with conventional monsters. In fact, he would not have used monsters at all; he would have made it a completely satisfactory setting, for his own delight. This did not make sense.

"Ourss!" the snakeman hissed, his head lifting above the water. Beyond him, other heads appeared in the water.

Mach realized why the pigheads had stopped their pursuit. Their territory ended where that of the snake-folk began.

He looked back, but saw the pigheads still cl.u.s.tered at the edge of the swamp. He would have to proceed forward.

"I'm going!" he said, and sloshed along the path. He had to slide his bare feet forward under the water to make sure the firm path continued, lest he get dunked again. He wasn't sure what the snakes would do to him if they caught him, but didn't care to find out.

Fortunately there was no pursuit. As he moved he continued to ponder. If this was not the kind of situation his robot brain would or could have created, how could he account for his dream? The answer was that he could not. But the alternative was to a.s.sume that it was not a dream. That suggested that it was reality.

Had he really been transported to the land he had sought, Phaze? By switching places with his twin? Of course a physical exchange could not have occurred. But a mental one-that did seem plausible. His consciousness was in the body of his twin-and his twin's consciousness must be in Mach's own body.

Mach's lips pursed in a soundless whistle. This thesis was reasonable-but what would a human person do in the body of a machine?

The path led to an island rising out of the swamp. Relieved, Mach sloshed toward it-and stepped off the path again, taking another messy dunking. The path curved about, as it had on land, and he had to check for it constantly.

He drew himself out of the muck, then proceeded to the island. It was thickly overgrown with reeds and brush and small trees, but the path was clear. This was certainly better than the water.

Mach rounded a bend-and came across a worse monster than before. It was a man-with the head of a giant roach. The antennae waved and the complicated insectoid mouth-parts quivered. The thing looked hungry.

Mach backed away-but another roach-head came onto the path behind him. He was trapped.

Well, not quite. He leaped into the brush to the side. Too late he discovered that it was solid brambles; the thorns raked along his legs and torso stingingly. Yet the roach-heads were blocking the path, their ugly mandibles working. He had not been programmed to abhor roaches; indeed, they did not exist in the natural state in the frame of Proton. But his living body evidently loathed the notion of contact with such creatures, and certainly he didn't want those mandibles chewing into his tender flesh.

Trapped between unacceptable alternatives, Mach let his body govern. His head went back and he screamed. "Heeelp!"

There was a distant sound of music. Then an approaching beat. It sounded as if a horse were approaching.

Mach screamed again. He knew how to ride a horse; that was one of the Game challenges. If the creature were tame, or even if it weren't-if he could somehow get on it-but of course it was tame, for he heard the music of the rider.

In a very brief time the beat became splashing. The horse was charging through the water. Maybe there was a patrol whose duty was to come to the aid of distressed travelers. Mach called again, making sure the rider could find him.

Now it thundered onto the island, the music of its rider becoming loud. It sounded as though a flute were playing, or several of them. The roach-heads abruptly scuttled into the brush, apparently not bothered by the brambles.

"Here!" Mach cried.

The horse came into sight.

It bore no rider. It was glossy black, with golden socklike coloration on the two hind legs. From the forehead sprouted a long spiraled horn.

This was a unicorn.

Mach was beyond caring at this point. "I beg you, beautiful creature-carry me from here!" he called.

The unicorn stopped. It was a mare, not large for a horse, but in fit condition. Her head turned toward Mach. She sounded a double note of query.

The horn was making the music! Citizen Blue had mentioned this, long ago, but Mach had a.s.sumed this was mere embellishment of a tale told to a child. Now he realized that it was literal. His father had come from this frame, and had known unicorns.

Mach pulled himself painfully from the brambles. His body was bleeding in several places. "If you will carry me-" he repeated, afraid the mare would bolt before he could mount her.

But she made an acquiescent note. He came up to her and scrambled onto her back, taking firm hold of her glossy mane. "My grat.i.tude to you, lovely creature!" he gasped.

She started walking, then trotting, wending her way on along the narrow path with sure-footed confidence. As she moved, she played a pretty double melody on her marvelous horn. Mach was good at music, both because he had been programmed for perfect pitch and because it was a useful talent in the Game; he knew quality when he heard it, and that horn was as good as an instrument could be. To think that a mere animal could do it so well! There was no further sign of the roach-heads; evidently the music warned them away.

The path proceeded to the other side of the island and back into the water. The animal trod it with confidence, evidently knowing exactly where to place he: hooves. The water swirled with fish, some of them large three vertical fins cut through the ripples toward them. The unicorn pointed her horn at the largest and blew triple-note chord of warning; the fin altered course immediately, approaching no closer, and the other two did likewise.

Farther along a thing like a crocodile lifted its Ion, snout, hissing. Again the unicorn blew her chord, and the thing backpedaled. Mach was impressed; it was evident that this equine creature was not to be trifled with. How fortunate that she had come to his rescue!

But why had she done so? Mach remembered that his father had spoken of a.s.sociating with a unicorn. Or his alternate self had done so. But he had never provided any details. "That life is past," was all he would ever say. Mach had gathered that unicorns were not necessarily friendly to man; apparently it had been a remarkable thing for a man to befriend one. Yet this one had come right to him, a stranger, and rescued him.

The water-path was finally headed for solid land again. Here the footing seemed to be especially intricate; the unicorn was almost doing a four-footed dance as she stepped along it. And here it was that a more formidable menace appeared.

From the deep water to the side emerged a huge and mottled reptilian head. It had two curling horns and greenish scales and widely spreading whiskers. Then the mouth opened, to reveal an array of teeth as formidable as any Mach had known of. Jets of steam issued from the metallic nostrils, forming swirling little clouds as they cooled and expanded.

The unicorn paused. It was evident that this was a threat she did not dismiss lightly. Indeed, as the monster lifted itself higher, Mach could see why. This was a literal dragon!

The dragon leaned forward, extending two front legs with ferocious talons. Its head swung on a sinuous neck. More steam issued, forming cloudlets bathing Mach with hot vapor. Viscous saliva dripped from the mouth.

The unicorn tilted her head so that her right eye bore directly on Mach, as if questioning him. He shrugged nervously. "If you don't know what to do, I certainly don't!" he said. He had been gaining confidence as the animal bore him to safety; now that confidence was rapidly draining away. He realized that the unicorn could not readily back away; the footing was so tricky that she probably had to move forward to achieve it. On land she could have fled the dragon; here she could not. Since it evidently had no fear of her horn, and appeared to be quite capable of destroying her in combat, this was a formidable threat.

The unicorn made something very like a shrug; the skin of her shoulders rippled. Then she faced the dragon and blew a new chord. This seemed to have about four notes, with a quaver and an especially penetrating quality; it made a shiver run down Mach's back.

The dragon paused. Then it snorted more steam and cranked its jaws farther open. The gape of that mouth was horrendous; Mach realized that the dragon could snap off half his body with one bite, and perhaps intended to do just that. The unicorn's chord of warning had not dissuaded it. This monster knew it commanded the situation, and it was hungry, and it intended to feed. Mach's living heart was beating at a fast rate, and his living breathing was becoming noisy. He was afraid-if and this was an emotion he had never before experienced. He did not enjoy it.

The unicorn blew her chord again, louder. Again the dragon paused, the little ears below its horns swiveled to orient on that sound. Evidently the chord was a special type of signal, that did have some effect-but not enough to put this monster off entirely.

The dragon brought its head slowly down. The big nostrils pointed at Mach like the barrels of twin rifles. The torso expanded; evidently the dragon was taking deep breath, getting ready to issue a blast of steam that would cook man and unicorn in place.

The unicorn took her own deep breath. She set her self, pointed her horn straight up, and stretched out her neck. The hairs of her mane lifted, almost like the hackles of an angry dog. There was going to be one phenomenally loud sound!

Abruptly the dragon backed away. Its head traveled to the side and down to the water, and under the surface, and the sinuous neck and body followed. In a moment it was gone.

Mach relaxed quiveringly. The mare had bluffed the dragon away! For some reason the monster had feared the threatened loud sound more than the lesser sounds.

The unicorn resumed her motion along the path, picking her way toward the land. While she did this, Mach pondered the matter further. Surely the louder chord could not have hurt the dragon, if the fainter ones had not. Why, then, had it retreated?

His living brain was not as straightforward about logic as his robot brain had been, but this was not a difficult process. Obviously the chord was not a weapon in itself, but a signal-a call for help. Thus a faint one served as a warning, while a loud one would be heard all over the forest and bring reinforcements. Other unicorns, perhaps. One dragon might overcome one immobilized unicorn, but suppose several unicorns came? Yet the dragon had disappeared so swiftly and completely into the water that it was hard to see how other unicorns could have come in time to help, or how they could have located the dragon for revenge if they came too late to save their companion. So this didn't make complete sense.

The unicorn reached land and picked up speed, resuming her trot. She resumed her melody; evidently she liked trotting to music. Where was she taking him? And why? She had put herself in real jeopardy to help him; why do this for a stranger? His logical mind struggled to make sense of things.

The path divided; without hesitation the animal selected one fork and trotted on. The forest was thinning now, with larger glades appearing, and finally open fields. They were ascending a slope that seemed to have no end; the unicorn's body became warmer from the exertion, but she did not sweat.

Now the land fell away on either side; the path was mounting a ridge, perhaps a glacial moraine. It was hard to tell, because time had pa.s.sed and dusk was closing; he could not see clearly to the base of the slopes. In due course they reached a ragged cliff; the path cut its way through to an interior crater that was open to the sky but otherwise closed. Here at last they stopped.

Mach slid off, glad to return to his own feet. He winced as he landed; he had forgotten the abrasion his soles had incurred. Also, his scratches stung. The interest of the ride had distracted him from such details, but now they intruded.

"Well, we are evidently here," he said. "But I don't know why you brought me, and I don't suppose you can explain."

The unicorn eyed him-and suddenly he had an ugly thought. Horses grazed on gra.s.s and ate grain and hay. What did unicorns eat? He had seen enough to know that their metabolism was not at all like that of mundane equines. Had this one brought him here-as prey?

The unicorn lowered her horn and stepped toward him. Abruptly terrified, Mach tried to run. But there was nowhere to run to; this was a closed region, with the unicorn blocking the only exit. He tried to climb the wall, but found no suitable handholds. He sc.r.a.ped his fingers against the stone in his desperate effort, incurring more scratches. He knew he was reacting foolishly, only making himself seem more like prey, but he had no automatic control over the emotion of this living body.

It was no use. If he was here to be eaten, he would just have to accept it. Defeated, he slumped against the stone wall, waiting for whatever was to come.

Nothing came. After a moment he turned around. The unicorn was gone.

She had brought him here-and left him. What did that mean? He wasn't sure that he cared to guess.

His palpitating bodily processes settled down somewhat. His more sensible mind rea.s.serted itself. He explored his prison. There was a mound of soft brush and hay at one side, evidently a sleeping place. This must be the unicorn's lair, protected from most other creatures. He was relieved to discover no bones; if she brought victims here for leisurely consumption, there should be bones.

He considered trying to escape, but he was now so tired that he knew he would not get far. Tiredness was another new phenomenon for him, and he didn't like it. And what was there for him outside? A jagged path, and a series of predatory monsters! Better to remain here and get some rest, and hope that the unicorn was after all beneficent.

He sat on the nest of brush. It was surprisingly comfortable. He leaned back against it. Before he knew it, he was asleep.

He woke in starry darkness. Something was wrong with his abdominal circuitry. He felt bloated. Had an oil valve clogged?

He checked at a service aperture, but found none; his fingers slid across unbroken skin. Then he remembered: he was in a living body!

That meant that he needed to release fluid, in the living manner. His robot body could eat and drink, but did not eliminate in the biological way; it simply regurgitated the material at a convenient time. Now he would have to perform in the fashion he had observed in human beings and androids.

He got up-and discovered that he was not alone. His hand brushed across the torso of another living creature. The unicorn?

He peered, and made out the vague outline. Not an animal, but a man! His hand helped define the leg, arm, breast- It was female!

Mach withdrew. Evidently he had not awakened her, and that was probably best. How had she come here?

She must have walked up the path, arriving after he was asleep. Perhaps this was where she regularly spent the night. She had seen him, and had simply settled down beside. him.

That seemed too simple, but it would have to do for now. He needed to find a suitable place to relieve himself.

He felt about with his feet, but knew that there was no place within this enclosure. He would have to go outside. So he walked carefully in the direction he remembered the entrance to be, and found the wall. The starlight from above did help. He moved along the wall, finding the exit. A gentle breeze gusted through it, refreshingly cool. In the distance was the sound of some night bird.

He established himself at the edge of the path, aimed his liquid-disposal appendage, and let go down the mountainside. It was a great relief. However, this reminded him of his thirst, which had not really been slaked at the swamp, and this now manifested with renewed force. Another problem of the living state!

He returned inside the crater. He would just have to sleep until morning, and then see what offered. Perhaps the human female would know where there was water. And food-he would be hungry soon.

But as he came to the brush pile, he realized that the female was awake. Indeed, she was sitting up, peering at him.

"I-I was uncomfortable," he said awkwardly. Natural functions were normally not discussed between the s.e.xes in Proton, and he a.s.sumed it was the same here.

"Bane," she said. Her voice was pleasant, having an almost flutelike quality.

"I don't understand."