Arm of the Law by Harry Harrison - At one time—this was before the Robot Restriction Laws—they'd even allowed them to make their own decisions....

It was a big, coffin-shaped plywood box that looked like it weighed a ton. This brawny type just dumped it through the door of the police station and started away. I looked up from the blotter and shouted at the trucker's vanishing back.

"What the hell is that?"

"How should I know?" he said as he swung up into the cab. "I just deliver, I don't X-ray 'em. It came on the morning rocket from earth is all I know." He gunned the truck more than he had to and threw up a billowing cloud of red dust.

"Jokers," I growled to myself. "Mars is full of jokers."

When I went over to look at the box I could feel the dust grate between my teeth. Chief Craig must have heard the racket because he came out of his office and helped me stand and look at the box.

"Think it's a bomb?" he asked in a bored voice.

"Why would anyone bother—particularly with a thing this size? And all the way from earth."

He nodded agreement and walked around to look at the other end. There was no sender's address anywhere on the outside. Finally we had to dig out the crowbar and I went to work on the top. After some prying it pulled free and fell off.

That was when we had our first look at Ned. We all would have been a lot happier if it had been our last look as well. If we had just put the lid back on and shipped the thing back to earth! I know now what they mean about Pandora's Box.

But we just stood there and stared like a couple of rubes. Ned lay motionless and stared back at us.

"A robot!" the Chief said.

"Very observant; it's easy to see you went to the police academy."

"Ha ha! Now find out what he's doing here."