The sign on the wall seemed to quaver under a film of slidingwarm water, Eckels felt his eyelids blink over his stare,and the sign burned in this momentary darkness:TIME SAFARI, INC.SAFARIS TO ANY YEAR IN THE PAST.YOU NAME THE ANIMAL.WE TAKE YOU THERE.YOU SHOOT IT.A warm phlegm gathered in Eckels' throat; he swallowedand pushed it down. The muscles around his mouth formeda smile as he put his hand slowly out upon the air, and inthat hand waved a check for ten thousand dollars to theman behind the desk.

"Does this safari guarantee I come back alive?"

"We guarantee nothing," said the official, "except thedinosaurs." He turned. "This is Mr. Travis, your SafariGuide in the Past. He'll tell you what and where to shoot.If he says no shooting, no shooting. If you disobey instructions, there's a stiff penalty of another ten thousand dollars,plus possible government action, on your return."Eckels glanced across the vast office at a mass and tangle,a snaking and humming of wires and steel boxes, at anaurora that flickered now orange, now silver, now blue.There was a sound like a gigantic bonfire burning all ofTime, all the years and all the parchment calendars, all thehours piled high and set aflame.A touch of the hand and this burning would, on the instant, beautifully reverse itself. Eckels remembered thewording in the advertisements to the letter. Out of charsand ashes, out of dust and coals, like golden salamanders,the old years, the green years, might leap; roses sweetenthe air, white hair turn Irish-black, wrinkles vanish; all,everything fly back to seed, flee death, rush down to theirbeginnings, suns rise in western skies and set in gloriouseasts, moons eat themselves opposite to the custom, all andeverything cupping one in another like Chinese boxes, rabbitsin hats, all and everything returning to the fresh death,the seed death, the green death, to the time before thebeginning. A touch of a hand might do it, the merest touchof a hand.

"Hell and damn," Eckels breathed, the light of theMachine on his thin face. "A real Time Machine." He shook hishead. "Makes you think. If the election had gone badlyyesterday, I might be here now running away from the results.Thank God Keith won. He'll make a fine President of theUnited States."

"Yes," said the man behind the desk. "Were lucky. IfDeutscher had gotten in, we'd have the worst kind of dictatorship. There's an anti-everything man for you, amilitarist, anti-Christ, anti-human, anti-intellectual. People called us up, you know, joking but not joking. Said ifDeutscher became President they wanted to go live in 1492.Of course it's not our business to conduct Escapes, but toform Safaris. Anyway, Keith's President now. All you got toworry about is"

"Shooting my dinosaur," Eckels finished it for him.

"A Tyrannosaurus Rex. The Thunder Lizard, the damnedestmonster in history. Sign this release. Anything happensto you, we're not responsible. Those dinosaurs are hungry."Eckels flushed angrily. "Trying to scare me!"

"Frankly, yes. We don't want anyone going who'll panicat the first shot. Six Safari leaders were killed last year, anda dozen hunters. We're here to give you the damnedestthrill a real hunter ever asked for. Travelling you back sixtymillion years to bag the biggest damned game in all Time.Your personal check's still there. Tear it up."Mr. Eckels looked at the check for a long time. Hisfingers twitched.

"Good luck," said the man behind the desk. "Mr. Travis,he's all yours."They moved silently across the room, taking their gunswith them, toward the Machine, toward the silver metaland the roaring light.First a day and then a night and then a day and then anight, then it was day-night-day-night-day. A week, amonth, a year, a decade! A.D. 2055. A.D. zoic). 1999! 1957!Gone! The Machine roared.They put on their oxygen helmets and tested the intercoms.Eckels swayed on the padded seat, his face pale, hisjaws stiff. He felt the trembling in his arms and he lookeddown and found his hands tight on the new rifle. Therewere four other men in the Machine. Travis, the SafariLeader, his assistant, Lesperance, and two other hunters,Billings and Kramer. They sat looking at each other, andthe years blazed around them.

"Can these guns get a dinosaur cold?" Eckels felt hismouth saying.

"If you hit them right," said Travis on the helmet radio.

"Some dinosaurs have two brains, one in the head, anotherfar down the spinal column. We stay away from those.That's stretching luck. Put your first two shots into the eyes,if you can, blind them, and go back into the brain."The Machine howled. Time was a film run backward.Suns fled and ten million moons fled after them. "GoodGod," said Eckels. "Every hunter that ever lived would envyus today. This makes Africa seem like Illinois."The Machine slowed; its scream fell to a murmur. TheMachine stopped.The sun stopped in the sky.The fog that had enveloped the Machine blew away andthey were in an old time, a very old time indeed, threehunters and two Safari Heads with their blue metal gunsacross their knees.

"Christ isn't born yet," said Travis. "Moses has not goneto the mountain to talk with God. The Pyramids are still inthe earth, waiting to be cut out and put up. Remember that,Alexander, Caesar, Napoleon, Hitler, none of them exists."The men nodded.

"That" Mr. Travis pointed" is the jungle of sixty milliontwo thousand and fifty-five years before President Keith."He indicated a metal path that struck off into greenwilderness, over steaming swamp, among giant ferns andpalms.

"And that," he said, "is the Path, laid by Time Safari foryour use. It floats six inches above the earth. Doesn't touchso much as one grass blade, flower, or tree. It's an anti-gravity metal. Its purpose is to keep you from touching thisworld of the past in any way. Stay on the Path. Don't gooff it. I repeat. Don't go off. For any reason! If you fall off,there's a penalty. And don't shoot any animal we don'tokay."

"Why?" asked Eckels.They sat in the ancient wilderness. Far birds' cries blewon a wind, and the smell of tar and an old salt sea, moistgrasses, and flowers the colour of blood.

"We don't want to change the Future. We don't belonghere in the Past. The government doesn't like us here. Wehave to pay big graft to keep our franchise. A Time Machine is damn finicky business. Not knowing it, we mightkill an important animal, a small bird, a roach, a flower even,thus destroying an important link in a growing species."

"That's not clear," said Eckels.

"All right," Travis continued, "say we accidentally kill onemouse here. That means all the future families of this oneparticular mouse are destroyed, right?"

"Right."

"And all the families of the families of that one mouse!With a stamp of your foot, you annihilate first one, thena dozen, then a thousand, a million, a billion possible mice"

"So they're dead," said Eckels. "So what?"

"So what?" Travis snorted quietly. "Well, what about thefoxes that'll need those mice to survive? For want of tenmice, a fox dies. For want of ten foxes, a lion starves. Forwant of a lion, all manner of insects, vultures, infinite billions of life forms are thrown into chaos and destruction.Eventually it all boils down to this: fifty-nine million yearslater, a cave man, one of a dozen on the entire world, goeshunting wild boar or saber-tooth tiger for food. But you,friend, have stepped on all the tigers in that region. Bystepping on one single mouse. So the cave man starves. Andthe cave man, please note, is not just any expendable man,no I He is an entire future nation. From his loins would havesprung ten sons. From their loins one hundred sons, and thusonward to a civilisation. Destroy this one man, and youdestroy a race, a people, an entire history of life. It iscomparable to slaying some of Adam's grandchildren. The stompof your foot, on one mouse, could start an earthquake, theeffects of which could shake our earth and destinies downthrough Time, to their very foundations. With the deathof that one cave man, a billion others yet unborn arethrottled in the womb. Perhaps Rome never rises on itsseven hills. Perhaps Europe is forever a dark forest, andonly Asia waxes healthy and teeming. Step on a mouse andyou crush the Pyramids. Step on a mouse and you leaveyour print, like a Grand Canyon, across Eternity. QueenElizabeth might never be born, Washington might not crossthe Delaware, there might never be a United States at all.So be careful. Stay on the Path, Never step off!"

"I see," said Eckels. "Then it wouldn't pay for us even totouch the grass?"

"Correct. Crushing certain plants could add up infinitesimally. A little error here would multiply in sixty millionyears, all out of proportion. Of course maybe our theoryis wrong. Maybe Time can't be changed by us. Or maybeit can be changed only in little subtle ways. A dead mousehere makes an insect imbalance there, a population disproportion later, a bad harvest further on, a depression, massstarvation, and, finally, a change in social temperament infar-flung countries. Something much more subtle, like that.Perhaps only a soft breath, a whisper, a hair, pollen on theair, such a slight, slight change that unless you looked closeyou wouldn't see it. Who knows? Who really can say heknows? We don't know. We're guessing. But until we doknow for certain whether our messing around in Time canmake a big roar or a little rustle in history, we're beingdamned careful. This Machine, this Path, your clothing andbodies, were sterilised, as you know, before the journey. Wewear these oxygen helmets so we can't introduce our bacteria into an ancient atmosphere."

"How do we know which animals to shoot?"

"They're marked with red paint," said Travis. "Today, beforeour journey, we sent Lesperance here back with theMachine. He came to this particular era and followedcertain animals."

"Studying them?"

"Right," said Lesperance. "I track them through theirentire existence, noting which of them lives longest. Very few.How many times they mate. Not often. Life's short. WhenI find one that's going to die when a tree falls on him, orone that drowns in a tar pit, I note the exact hour, minute,and second. I shoot a paint bomb. It leaves a red patchon his hide. We can't miss it. Then I correlate our arrivalin the Past so that we meet -the Monster not more than twominutes before he would have died anyway. This way, wekill only animals with no future, that are never going tomate again. You see how careful we are?"

"But if you came back this morning in Time," said Eckelseagerly, "you must've bumped into us, our Safari] How didit turn out? Was it successful? Did all of us get through-alive?"Travis and Lesperance gave each other a look.

"That'd be a paradox," said the latter. "Time doesn'tpermit that sort of mess a man meeting himself. When suchoccasions threaten, Time steps aside. Like an airplanehitting an air pocket. You felt the Machine jump just beforewe stopped? That was us passing ourselves on the wayback to the Future. We saw nothing. There's no way oftelling if this expedition was a success, if we got our monster, or whether all of us meaning you, Mr. Eckels, got outalive."Eckels smiled palely.

"Cut that," said Travis sharply. "Everyone on his feet!"They were ready to leave the Machine.The jungle was high and the jungle was broad and thejungle was the entire world forever and forever. Soundslike music and sounds like flying tents filled the sky, andthose were pterodactyls soaring with cavernous grey wings,gigantic bats out of a delirium and a night fever. Eckels,balanced on the narrow Path, aimed his rifle playfully.

"Stop that!" said Travis. "Don't even aim for fun, damnit! If your gun should go off"Eckels flushed. "Where's our Tyrannosaurus?"Lesperance checked his wrist watch. "Up ahead. Wellbisect his trail in sixty seconds. Look for the red paint, forChrist's sake. Don't shoot till we give the word. Stay onthe Path. Stay on the pathThey moved forward in the wind of morning.

"Strange," murmured Eckels. "Up ahead, sixty millionyears, Election Day over. Keith made President. Everyonecelebrating. And here we are, a million years lost, and theydon't exist. The things we worried about for months, alife-time, not even born or thought about yet."

"Safety catches off, everyone!" ordered Travis. "You, firstshot, Eckels. Second, Billings. Third, Kramer."

"I've hunted tiger, wild boar, buffalo, elephant, but Jesus,this is it," said Eckels. "I'm shaking like a kid."

"Ah," said Travis.Everyone stopped.Travis raised his hand. "Ahead," he whispered. "In themist. There he is. There's His Royal Majesty now."The jungle was wide and full of twitterings, rustlings,murmurs, and sighs.Suddenly it all ceased, as if someone had shut a door.Silence.A sound of thunder.Out of the mist, one hundred yards away, cameTyrannosaurus Rex.

"Jesus God," whispered Eckels.

"Shit"It came on great oiled, resilient, striding legs. It loweredthirty feet above half of the trees, a great evil god, foldingits delicate watchmaker's claws close to its oily reptilianchest. Each lower leg was a piston, a thousand pounds ofwhite bone, sunk in thick ropes of muscle, sheathed overin a gleam of pebbled skin like the mail of a terriblewarrior, Each thigh was a ton of meat, ivory, and steel mesh.And from the great breathing cage of the upper body thosetwo delicate arms dangled out front, arms with handswhich might pick up and examine men like toys, while thesnake neck coiled. And the head itself, a ton of sculpturedstone, lifted easily upon the sky. Its mouth gaped, exposinga fence of teeth like daggers. Its eyes rolled, ostrich eggs,empty of all expression save hunger. It closed its mouth ina death grin. It ran, its pelvic bones crushing aside treesand bushes, its taloned feet clawing damp earth, leavingprints six inches deep wherever it settled its weight. It ranwith a gliding ballet step, far too poised and balanced forits ten tons. It moved into a sunlit arena warily, its beautiful reptile hands feeling the air.

"My God!" Eckels twitched his mouth. "It could reachup and grab the moon."

"Shit" Travis jerked angrily. "He hasn't seen us yet."

"It can't be killed." Eckels pronounced this verdictquietly, as if there could be no argument. He had weighedthe evidence and this was his considered opinion. Therifle in his hands seemed a cap gun. "We were fools tocome. This is impossible."

"Shut up!" hissed Travis.

"Nightmare."

"Turn around," commanded Travis. "Walk quietly tothe Machine. We'll remit one-half your fee."

"I didn't realise it would be this big," said Eckels. "Imiscalculated, that's all. And now I want out."

"It sees us!"

"There's the red paint on its chest!"The Thunder Lizard raised itself. Its armoured flesh glittered like a thousand green coins. The coins, crusted withslime, steamed. In the slime, tiny insects wriggled, so thatthe entire body seemed to twitch and undulate, even whilethe monster itself did not move. It exhaled. The stink ofraw flesh blew down the wilderness.

"Get me out of here," said Eckels. "It was never like thisbefore, I was always sure I'd come through alive, I hadgood guides, good safaris, and safety. This time, I figuredwrong. I've met my match and admit it. This is too muchfor me to get hold of."

"Don't run," said Lesperance. "Turn around. Hide in theMachine."

"Yes." Eckels seemed to be numb. He looked at his feetas if trying to make them move. He gave a grunt ofhelplessness.

"Eckels"He took a few steps, blinking, shuffling.

"Not that way!"The Monster, at the first motion, lunged forward witha terrible scream. It covered one hundred yards in fourseconds. The rifles jerked up and blazed fire. A windstormfrom the beast's mouth engulfed them in the stench of slimeand old blood. The Monster roared, teeth glittering withsun.Eckels, not looking back, walked blindly to the edge ofthe Path, his gun limp in his arms, stepped off the Path, andwalked, not knowing it, in the jungle. His feet sank intogreen moss. His legs moved him, and he felt alone andremote from the events behind.The rifles cracked again. Their sound was lost in shriekand lizard thunder. The great lever of the reptile's tailswung up, lashed sideways. Trees exploded in clouds ofleaf and branch. The Monster twitched its jeweller's handsdown to fondle at the men, to twist them in half, to crushthem like berries, to cram them into its teeth and its screaming throat. Its boulder-stone eyes levelled with the men.They saw themselves mirrored. They fired at the metalliceyelids and the blazing black iris.Like a stone idol, like a mountain avalanche, Tyrannosaurs fell. Thundering, it clutched trees, pulled them withit. It wrenched and tore the metal Path, The men flungthemselves back and away. The body hit, ten tons of coldflesh and stone. The guns fired. The Monster lashed itsarmoured tail, twitched its snake jaws, and lay still. A fountof blood spurted from its throat. Somewhere inside, a sacof fluids burst. Sickening gushes drenched the hunters. Theystood, red and glistening.The thunder faded.The jungle was silent. After the avalanche, a green peace.After the nightmare, morning.Billings and Kramer sat on the pathway and threw up.Travis and Lesperance stood with smoking rifles, cursingsteadily.In the Time Machine, on his face, Eckels lay shivering.He had found his way back to the Path, climbed into theMachine.Travis came walking, glanced at Eckels, took cottongauze from a metal box, and returned to the others, whowere sitting on the Path.

"Clean up."They wiped the blood from their helmets. They beganto curse too. The Monster lay, a hill of solid flesh. Within,you could hear the sighs and murmurs as the furthest chambers of it died, the organs malfunctioning, liquids runninga final instant from pocket to sac to spleen, everythingshutting off, closing up forever. It was like standing by awrecked locomotive or a steam shovel at quitting time, allvalves being released or levered tight. Bones cracked; thetonnage of its own flesh, off balance, dead weight, snappedthe delicate forearms, caught underneath. The meat settled,quivering.Another cracking sound. Overhead, a gigantic tree branchbroke from its heavy mooring, fell. It crashed upon thedead beast with finality.

"There." Lesperance checked his watch. "Right on time.That's the giant tree that was scheduled to fall and killthis animal originally." He glanced at the two hunters.

"You want the trophy picture?"

"What?"

"We can't take a trophy back to the Future. The bodyhas to stay right here where it would have died originally,so the insects, birds, and bacteria can get at it, as they wereintended to. Everything in balance. The body stays. Butwe can take a picture of you standing near it."The two men tried to think, but gave up, shaking theirheads.They let themselves be led along the metal Path. Theysank wearily into the Machine cushions. They gazed backat the ruined Monster, the stagnating mound, where alreadystrange reptilian birds and golden insects were busy at thesteaming armour.A sound on the floor of the Time Machine stiffened them.Eckels sat there, shivering.

"I'm sorry," he said at last.

"Get up!" cried Travis.Eckels got up.

"Go out on that Path alone," said Travis. He had his riflepointed. "You're not coming back in the Machine. We'releaving you here!"Lesperance seized Travis' arm. "Wait"

"Stay out of this!" Travis shook his hand away. "This sonof a bitch nearly killed us. But it isn't that so much. Hell, no.It's his shoes Look at them! He ran off the Path. My God,that ruins us I Christ knows how much we'll forfeit. Tens ofthousands of dollars of insurance We guarantee no oneleaves the Path. He left it. Oh, the damn fool! Ill have toreport to the government. They might revoke our licenseto travel. God knows what he's done to Time, to History!"

"Take it easy, all he did was kick up some dirt."

"How do we know?" cried Travis. "We don't know anything!It's all a damn mystery! Get out there, Eckels!"Eckels fumbled his shirt. "Ill pay anything. A hundredthousand dollars!"Travis glared at Eckels' chequebook and spat. "Go outthere. The Monster's next to the Path. Stick your arms upto your elbows in his mouth. Then you can come back withus."

"That's unreasonable!"

"The Monsters dead, you yellow bastard. The bullets!The bullets can't be left behind. They don't belong in thePast; they might change something. Here's my knife. Digthem out!"The jungle was alive again, full of the old tremoringsand bird cries. Eckels turned slowly to regard that primevalgarbage dump, that hill of nightmares and terror. After along time, like a sleepwalker, he shuffled out along the Path.He returned, shuddering, five minutes later, his armssoaked and red to the elbows. He held out his hands. Eachheld a number of steel bullets. Then he fell. He lay wherehe fell, not moving.

"You didn't have to make him do that," said Lesperance.

"Didn't I? It's too early to tell." Travis nudged the stillbody. "He'll live. Next time he won't go hunting game likethis. Okay." He jerked his thumb wearily at Lesperance.

"Switch on. Let's go home."1492. 1776. 1812.They cleaned their hands and faces. They changed theircaking shirts and pants. Eckels was up and around again,not speaking. Travis glared at him for a full ten minutes.

"Don't look at me," cried Eckels. "I haven't done anything."

"Who can tell?"

"Just ran off the Path, that's all, a little mud on my shoeswhat do you want me to get down and pray?"

"We might need it. I'm warning you, Eckels, I might killyou yet. I've got my gun ready."

"I'm innocent. I've done nothing]"1999. 2000. 2055.The Machine stopped.

"Get out," said Travis.The room was there as they had left it. But not the sameas they had left it. The same man sat behind the same desk.But the same man did not quite sit behind the same desk.Travis looked around swiftly. "Everything okay here?" hesnapped.

"Fine. Welcome home!"Travis did not relax. He seemed to be looking at the veryatoms of the air itself, at the way the sun poured throughthe one high window.

"Okay, Eckels, get out. Don't ever come back."Eckels could not move.

"You heard me," said Travis. "What're you staring at?"Eckels stood smelling of the air, and there was a thing tothe air, a chemical taint so subtle, so slight, that only a faintcry of his subliminal senses warned him it was there. Thecolours, white, grey, blue, orange, in the wall, in the furniture,in the sky beyond the window, were . . . were . . .And there was a feel. His flesh twitched. His hands twitched.He stood drinking the oddness with the pores of his body.Somewhere, someone must have been screaming one ofthose whistles that only a dog can hear. His body screamedsilence in return. Beyond this room, beyond this wall, beyondthis man who was not quite the same man seated atthis desk that was not quite the same desk . . . lay an entireworld of streets and people. What sort of world it was now,there was no telling. He could feel them moving there, beyond the walls, almost, like so many chess pieces blownin a dry wind. . . .But the immediate thing was the sign painted on theoffice wall, the same sign he had read earlier today on firstentering.Somehow, the sign had changed:TYME SEFARI INC.SEFARIS TU ANY YEEH EN THE PAST.YU NAIM THE ANIMALL.WEE TAEK YOU THAIR.YU SHOOT ITT.Eckels felt himself tall into a chair. He fumbled crazilyat the thick slime on his boots. He held up a clod of dirt,trembling. "No, it can't be. Not a little thing like that. No!"Embedded in the mud, glistening green and gold andblack, was a butterfly, very beautiful, and very dead.

"Not a little thing like that! Not a butterfly!" criedEckels.It fell to the floor, an exquisite thing, a small thing thatcould upset balances and knock down a line of smalldominoes and then big dominoes and then gigantic dominoes,all down the years across Time. Eckels' mind whirled. Itcouldn't change things. Killing one butterfly couldn't be thatimportant! Could it?His face was cold. His mouth trembled, asking: "Whowon the presidential election yesterday?"The man behind the desk laughed. "You joking? Youknow damn well. Deutscher, of course! Who else? Not thatdamn weakling Keith. We got an iron man now, a manwith guts, by God!" The official stopped. "What's wrong?"Eckels moaned. He dropped to his knees. He scrabbledat the golden butterfly with shaking fingers. "Can't we," hepleaded to the world, to himself, to the officials, to theMachine, "can't we take it back, can't we make it aliveagain? Can't we start over? Can't we"He did not move. Eyes shut, he waited, shivering. Heheard Travis breathe loud in the room; he heard Travisshift his rifle, click the safety catch, and raise the weapon.There was a sound of thunder.