He wasn't thinking of anything in particular, just relaxing against a building, waiting for a man. Greco didn't know why the man was to be killed. He didn't care. Greco's lack of curiosity was part of his value.

The other part was his skill.

One bullet, neatly placed in the head of a man he didn't know. It didn't excite him or sicken him. It was a job, just like anything else. You killed a man. So?

As Greco's victim stepped out of a building, Greco lifted the .45 out of his pocket. He released the safety and braced the gun with his right hand. He still wasn't thinking of anything as he took aim ...

And was knocked off his feet.

Greco thought he had been shot. He struggled up again, looked around, and sighted foggily on his victim.

Again he was knocked down.

This time he lay on the ground, trying to draw a bead. He never thought of stopping, for Greco was a craftsman.

With the next blow, everything went black. Permanently, because the watchbird's duty was to protect the object of violence--_at whatever cost to the murderer_.

The victim walked to his car. He hadn't noticed anything unusual.

Everything had happened in silence.

Gelsen was feeling pretty good. The watchbirds had been operating perfectly. Crimes of violence had been cut in half, and cut again. Dark alleys were no longer mouths of horror. Parks and playgrounds were not places to shun after dusk.

Of course, there were still robberies. Petty thievery flourished, and embezzlement, larceny, forgery and a hundred other crimes.

[Ill.u.s.tration]

But that wasn't so important. You could regain lost money--never a lost life.

Gelsen was ready to admit that he had been wrong about the watchbirds.

They _were_ doing a job that humans had been unable to accomplish.

The first hint of something wrong came that morning.

Macintyre came into his office. He stood silently in front of Gelsen's desk, looking annoyed and a little embarra.s.sed.

"What's the matter, Mac?" Gelsen asked.

"One of the watchbirds went to work on a slaughterhouse man. Knocked him out."

Gelsen thought about it for a moment. Yes, the watchbirds would do that.

With their new learning circuits, they had probably defined the killing of animals as murder.

"Tell the packers to mechanize their slaughtering," Gelsen said. "I never liked that business myself."

"All right," Macintyre said. He pursed his lips, then shrugged his shoulders and left.

Gelsen stood beside his desk, thinking. Couldn't the watchbirds differentiate between a murderer and a man engaged in a legitimate profession? No, evidently not. To them, murder was murder. No exceptions. He frowned. That might take a little ironing out in the circuits.

[Ill.u.s.tration]

But not too much, he decided hastily. Just make them a little more discriminating.

He sat down again and buried himself in paperwork, trying to avoid the edge of an old fear.

They strapped the prisoner into the chair and fitted the electrode to his leg.

"Oh, oh," he moaned, only half-conscious now of what they were doing.

They fitted the helmet over his shaved head and tightened the last straps. He continued to moan softly.

And then the watchbird swept in. How he had come, no one knew. Prisons are large and strong, with many locked doors, but the watchbird was there--

To stop a murder.

"Get that thing out of here!" the warden shouted, and reached for the switch. The watchbird knocked him down.

"Stop that!" a guard screamed, and grabbed for the switch himself. He was knocked to the floor beside the warden.

"This isn't murder, you idiot!" another guard said. He drew his gun to shoot down the glittering, wheeling metal bird.

Antic.i.p.ating, the watchbird smashed him back against the wall.

There was silence in the room. After a while, the man in the helmet started to giggle. Then he stopped.

The watchbird stood on guard, fluttering in mid-air--

Making sure no murder was done.

New data flashed along the watchbird network. Unmonitored, independent, the thousands of watchbirds received and acted upon it.

_The breaking, mangling or otherwise stopping the functions of a living organism by a living organism. New acts to stop._

"d.a.m.n you, git going!" Farmer Ollister shouted, and raised his whip again. The horse balked, and the wagon rattled and shook as he edged sideways.

"You lousy hunk of pigmeal, git going!" the farmer yelled and he raised the whip again.

It never fell. An alert watchbird, sensing violence, had knocked him out of his seat.

A living organism? What is a living organism? The watchbirds extended their definitions as they became aware of more facts. And, of course, this gave them more work.

The deer was just visible at the edge of the woods. The hunter raised his rifle, and took careful aim.

He didn't have time to shoot.