Step by step Lucky explained the control board. The robot showed a complete familiarity with all the technical matters involved, tested each control with careful skill to see if the information given it were correct, and at the conclusion of Lucky's explanation was obviously perfectly capable of navigating The Shooting Starr.

Lucky smiled and his eyes were lit with frank admiration.

Bigman pulled him off to their cabin. "What are you grinning for, Lucky?"

"Great Galaxy, Bigman, it's a beautiful machine. We've got to hand the Sirians credit for that. They can turn out robots that are works of art."

"Okay, but quiet, I don't want it to hear what I'm going to say. Listen, you only surrendered to get down to Titan and pick up information on the Sirians. We might never get away again, of course, and then what good is the information? But we've got this robot now. If we can get it to help us get away right now, then we've got what we want. The robot must have tons of information about the Sirians. We'll have more this way than if we land on Titan."

Lucky shook his head. "It sounds good, Bigman. But how do you expect to argue the robot into joining us?"

"First Law. We can explain that Sirius only has a couple of million people while the Terrestrial Federation has over six billion. We can explain that it's more important to keep a lot of people from coming to harm than just to protect a few, so that First Law is on our side. See, Lucky?"

Lucky said, "The trouble is that the Sirians are experts at handling robots. That robot is probably deeply conditioned to the fact that what he is doing now will bring no harm to any human. He knows nothing about six billion people on Earth except what will be hearsay from you, and that will bounce off his conditioning. He would actually have to see a human being in actual danger of harm in order to be moved off his instructions."

"I'm going to try."

"All right. Go ahead. The experience will do you good."

Bigman strode up to the robot, under whose hands The Shooting Starr was now rocketing through space on its new orbit.

He said, "What do you know of Earth, of the Terrestrial Federation?"

"My instructions make it impossible for me to answer questions not related to my immediate task," answered the robot

"I order you to ignore your previous instructions."

There was a momentary hesitation before the answer came. "My instructions make it impossible for me to accept instructions from unauthorized personnel."

"My orders are given you in order to prevent harm to human beings. They must therefore be obeyed," Bigman said.

"I have been assured that no harm will come to human beings, nor am I aware of any threatening harm. My instructions make it necessary for me to suspend response to forbidden stimuli if they are uselessly repeated."

"You better listen. There is harm intended." Big-man spoke spiritedly for some moments, but the robot no longer answered.

Lucky said, "Bigman, you're wasting effort."

Bigman kicked at the robot's gleaming ankle. He might as well have kicked the hull of the ship, for all the effect it had. He came toward Lucky, face red with anger. "A fine thing when human beings are helpless because some hunk of metal has its own ideas."

"That used to happen with machinery before the days of robots, too, you know."

"We don't even know where we're heading."

"We don't need the robot for that. I've been checking the course, and we're obviously heading for Titan."

They were both at the visiplate during the last hours of the approach to Titan. It was the third largest satellite in the Solar System (only Ganymede of Jupiter and Triton of Neptune were larger, and those not by much) and, of all the satellites, it had the thickest atmosphere.

The effect of its atmosphere was obvious even from a distance. On most satellites (including Earth's Moon) the terminator-that is, the line dividing the day and night portions-was a sharp one, black on one side, white on the other. But it was not so in this case.

Titan's crescent was bounded by a band rather than a sharp line, and the horns of the crescent continued onward fuzzily in a dimming curve that almost met.

"It has an atmosphere almost as thick as Earth's, Bigman," said Lucky.

"Not breathable?" said Bigman.

"No, not breathable. It's mainly methane."

Other ships were crowding in now, becoming visible to the naked eye. There were at least a dozen, herding them down the spaceways to Titan.

Lucky shook his head. "Twelve ships to spare for this one job. Great Galaxy, they must have been here for years, building and preparing. How can we ever get them off again, short of war?"

Bigman attempted no answer.

Again the sound of atmosphere made its unmistakable way into the ship,.the high-pitched keening of thin wisps of gas whipping past the streamlined hull.

Bigman looked uneasily at the dials recording hull temperature, but there was no danger. The robot at the controls was sure-handed. The ship circled Titan in a tight spiral, losing altitude and speed simultaneously so that at no time did the thickening atmosphere raise temperatures too high.

Again Lucky glowed with admiration. "It will manage it without fuel at all. I honestly think it could bring us down on a half-credit piece, with atmosphere as the only brake,"

Bigman said, "What's good about that, Lucky? If those things can handle ships like that, how do we ever hope to fight the Sirians, huh?"

"We'll just have to learn to build our own, Bigman. These robots are a human achievement. The humans that did the achieving are Sirians, yes, but they are human beings, too, and all other humans can share pride in the achievement. If we fear the results of their achievement, let's match it ourselves or more than match it. But there's no use denying them the worth of their accomplishment."

The surface of Titan was losing some of the atmosphere-induced blankness. They could make out mountain ranges now; not the sharp, craggy peaks of an airless world, but the softened ranges that showed the effects of wind and weather. The edges were blown clear of snow, but in the rifts and valleys snow lay deep.

"Not snow, really," said Lucky, "frozen ammonia."

All was desolate, of course. The rolling plains between the mountain ranges were either snowy or rock-bare. No life of any kind appeared. No rivers or lakes. And then…

"Great Galaxy!" said Lucky.

A dome had made its appearance. A flattened dome of a type familiar enough on the inner planets. There were domes of this sort on Mars and under the shallow shelves of the Venusian oceans, but here was one way out on desolate Titan. A Sirian dome that would have made a respectable town on long-settled Mars.

"We've slept while they've built," said Lucky.

"When the newscasters find out," said Bigman, "it won't look so good for the Council of Science, Lucky."

"Unless we break this thing, it won't. And the Council doesn't deserve better. Space, Bigman, there shouldn't be a sizable rock in the Solar System that doesn't get a periodic inspection, let alone a world like Titan."

"Who would have thought… "

"The Council of Science should have thought. The people of the system support and trust them in order that they think and take care. And I should have thought too."

The voice of the robot broke in upon them. "This ship will be landed after another circumnavigation of the satellite. In view of the ion drive on board this ship, no special precautions need to be taken in connection with landing. Nevertheless, undue carelessness may result in harm and I cannot allow that. I must therefore request you to lie down and strap yourselves in."

Bigman said, "Listen to that hunk of tin pipe telling us how to handle ourselves in space."

"Just the same," said Lucky, "you'd better lie down.