He thought now that it would be easier to flee this world than to dispose of two large, conspicuous corpses. But if he were already being watched?

They didn’t look like ARM agents. Large, soft in the muscle, pale from a sunlight more orange than yellow, they were certainly low-gravity types, probably Canyonites. They hadn’t fought like ARMs … but they had bypassed his alarms. These men could be ARM hirelings, with friends waiting.

Louis Wu disarmed his balcony door and stepped out.

Canyon does not quite follow the usual rules for planets.

The planet is not much bigger than Mars. Until a few hundred years ago its atmosphere was just dense enough to support photosynthesis-using plants. The air held oxygen, but was too thin for human or kzinti life. The native life was as primitive and hardy as lichen. Animal had never developed at all.

But there were magnetic monopoles in the cometary halo around Canyon’s orange-yellow. sun, and radioactives on the planet itself. The Kzinti Empire swallowed the planet and staffed it with the aid of domes and compressors. They called it Warhead, for its proximity to the unconquered Pierin worlds.

A thousand years later the expanding Kzinti Empire met human space.

The Man-Kzin wars were long over when Louis Wu was born. Men won them all. The kzinti have always had a tendency to attack before they are quite ready. Civilization on Canyon is a legacy of the Third Man-Kzin War, when the human world Wunderland developed a taste for esoteric weapons.

The Wunderland Treatymaker was used only once. It was a gigantic version of what is commonly a mining tool: a disintegrator that fires a beam to suppress the charge on the electron. Where a disintegrator beam falls, solid matter is rendered suddenly and violently positive. It tears itself into a fog of monatomic particles.

Wunderland built, and transported into the Warhead system, an enormous disintegrator firing in parallel with a similar beam to suppress the charge on the proton.

The two beams touched down thirty miles apart on Canyon’s surface. Rock and kzinti factories and housing spewed away as dust, and a solid bar of lightning flowed between the two points. The weapon chewed twelve miles deep into the planet, exposing magma throughout a region the size and shape of Baja California on Earth, and running roughly east and west. The kzinti industrial complex vanished. The few domes protected by stasis fields were swallowed by magma, magma that welled higher in the center of the great gash before the rock congealed.

The eventual result was a sea surrounded by sheer cliffs many miles high, surrounding in turn a long, narrow island.

Other human worlds may doubt that the Wunderland Treatymaker ended the war. The Kzinti Patriarchy is not normally terrified by sheer magnitude. Wunderlanders have no such doubts.

Warhead was annexed after the Third Man-Kzin War, and became Canyon. Canyon’s native life suffered, of course, from the gigatons of dust that dropped on its surface, and from the loss of water that precipitated within the canyon itself to form the sea. In the canyon there is comfortable air pressure and a thriving pocket-sized civilization.

Louis Wu’s apartment was twelve stories up the side of the north face of the canyon. Night shadowed the canyon floor as he stepped outside, but the southern face still glowed with daylight. Hanging gardens of native lichen dripped from the rim. Old elevators were silver threads standing miles high against the cut stone. Transfer booths had made these obsolete for travel, but tourists still used them for the view.

The balcony overlooked the belt of parkland that ran down the center of the island. The vegetation had the wild look of a kzinti hunting park, with pink and orange blended into the imported terrestrial biosphere. Kzinti life was common throughout the canyon.

There were as many kzinti as human tourists down there. The kzinti. males looked like fat orange cats walking on their hind legs … almost. But their ears flared like pink Chinese parasols, and their tails were nude and pink, and their straight legs and big hands marked them as toolmakers. They stood eight feet tall, and though they scrupulously avoided bumping human tourists, carefully tended claws slid out above black fingertips if a human passed too close. Reflex. Maybe.

Sometimes Louis wondered what impulse brought them back to a world once theirs. Some might have ancestors here, alive in frozen time in the domes buried beneath this lava island. One day they’d have to be dug up …

There were so many things he hadn’t done on Canyon, because the wire was always calling. Men and kzinti had climbed those sheer cliffs for sport, in the low gravity.

Well, he would have one last chance to try that. It was one of his three routes out. The second was the elevators; the third, a transfer booth to the Lichen Gardens. He’d never seen them.

Then overland in a pressure suit light enough to fold into a large briefcase.

On the surface of Canyon there were mines, and there was a large, indifferently tended preserve for the surviving varieties of Canyon lichen. But most of the world was barren moonscape. A careful man could land a spacecraft undetected, and could hide it where only a deep-radar search would find it. A careful man had. For these past nineteen years Louis Wu’s ship had been waiting, hidden in a cave in the northward-facing cliff of a mountain of low-grade metal ore: a hole hidden within permanent shadow on Canyon’s airless surface.

Transfer booths or elevators or cliff-climbing. Let Louis Wu get to the surface and he was home free. But the ARM could be watching all three exits.

Or he could be playing paranoid games with himself. How could Earth’s police force have found him? He had changed his face, his hair style, his way of life. The things he loved best were just the things he had given up. He used a bed instead of sleeping plates, he avoided cheese as if it were spoiled milk, and his apartment was furnished with mass-produced retractables. The only clothes he owned were of expensive natural fiber, with no optical effects at all.

He had left Earth as an emaciated and dreamy-eyed wirehead. Since then he had forced a rational diet on himself; he had tortured himself with exercise and a weekly course in martial arts (mildly illegal, and the local police would register him if they caught him, but not as Louis Wu!) until today he was an adequate facsimile of glowing health, with the hard muscles a younger Louis Wu had never bothered to attain. How could the ARM recognize him?

And how had they got in? No common burglar could have passed Louis’s alarms.

They lay dead in the grass, and soon the smell would overpower the air conditioning. Now, a bit late, he felt the shame of the man-killer. But they had invaded his territory, and there is no guilt under the wire. Even pain is a spice added to joy, and joy—like the basic human joy of killing a thief in the act—becomes hugely intensified. They had known what he was, and that was both sufficient warning and a direct affront to Louis Wu.

The kzinti and human tourists and natives milling in the street below looked innocent enough, and probably were. If an ARM was watching him now, it would be through binoculars, from a window in one of those black-eyed buildings. None of the tourists were looking up … but Louis Wu’s eyes found a kzin, and locked.

Eight feet tall, three feet broad, thick orange fur turning gray in spots: he was very like the dozens of kzinti about him. What caught Louis’s eye was the way the fur grew. It was tufted, patchy, and whitened over more than half the alien’s body, as if the skin below were extensively scarred. There were black markings around his eyes, and the eyes weren’t looking at scenery. They were searching the faces of passing humans.