Gladia said through her teeth, "Why didn't you run at the end and get help? Why did you remain helplessly watching?"
"Well," said D.G., with an attempt at the kind of lightness he would have showed easily were he feeling better, "with you refusing to leave Daneel, I rather hesitated to play the coward by comparison."
"You fool! I was safe. She would not have harmed me."
Daneel said, "Madam, it distresses me to contradict you, but I think she would have done so as her urge to destroy me grew stronger."
Gladia turned on him hotly. "And that was a smart thing you did, pushing me out of the way. Did you want to be destroyed?"
"Rather than see you harmed, madam, yes. My failure to stop the robot through inhibitions set up by her human appearance demonstrated, in any case, an unsatisfactory limit to my usefulness to you."
"Even so," said Gladia, "she would have hesitated to shoot me, since I am human, for a perceptible period of time and you could have had the blaster in your own possession by that time."
"I couldn't gamble your life, madam, on anything as uncertain as her hesitation," said Daneel.
"And you," said Gladia, showing no signs of having heard Daneel and turning to D.G. again, "shouldn't have brought the blaster in the first place."
D.G. said, frowning, "Madam, I am making allowances for the fact that we have all been very close to death. The robots do not mind that and I have grown somehow accustomed to danger. To you, however, this was an unpleasant novelty and you are being childish as a result. I forgive you - a little. But please listen. There was no way I could have known the blaster would be taken from me so easily Had I not brought the weapon, the overseer could have killed me with her bare hands as quickly and as effectively as she could have by blaster. Nor was there any point in my running, to answer an earlier complaint of yours. I could not outrun a blaster. Now please continue if you must still get it out of your system, but I do not intend to reason with you any further."
Gladia looked from D.G. to Daneel and back and said in a low voice, "I suppose I am being unreasonable. Very well, no more hind sights."
They had reached the ship. Crew members poured out at the sight of them. Gladia noticed they were armed.
D.G. beckoned to his second-in-command. "Oser, I presume you see that object the two robots are carrying?"
"Yes, sir."
"Well, have them carry it on board. Have it put in the security room and kept there. The security room is then to be locked and kept locked." He turned away for a moment, then turned back. "And Oser, as soon as that is done, we will prepare to take off again."
Oser said, "Captain, shall we keep the robots as well?"
"No. They are too simple in design to be worth much and, under the circumstances, taking them would create undesirable consequences. The device they are carrying is much more valuable than they are."
Giskard watched the device being slowly and very carefully maneuvered into the ship. He said, "Captain, I am guessing that that is a dangerous object."
"I'm under that impression, too," said D.G. "I suspect that the ship would have been destroyed soon after we were."
"That thing?" said Gladia. "What is it?"
"I can't be certain, but I believe it is a nuclear intensifier. I've seen experimental models on Baleyworld and this looks like a big brother."
"What is a nuclear intensifier?"
"As the name implies, Lady Gladia, it's a device that intensifies nuclear fusion."
"How does it do that?"
D.G. shrugged. "I'm not a physicist, my lady. A stream of W particles is involved and they mediate the weak interaction. That's all I know about it."
"What does that do?" asked Gladia.
"Well, suppose the ship has its power supply as it has right now, for instance. There are small numbers of protons, derived from our hydrogen fuel supply, that are ultrahot and fusing to produce power. Additional hydrogen is constantly being heated to produce free protons, which, when hot enough, also fuse to maintain that power. If the stream of W particles from the nuclear intensifier strikes the fusing protons, these fuse more quickly and deliver more heat. That heat produces protons and sets them to fusing more quickly than they should be and their fusion produces still more heat, which intensifies the vicious cycle. In a tiny fraction of a second, enough of the fuel fuses to form a tiny thermonuclear bomb and the entire ship and everything upon it is vaporized.
Gladia looked awed. "Why doesn't everything ignite? Why doesn't the whole planet blow up?"
"I don't suppose there's danger of that, madam. The protons have to be ultrahot and fusing. Cold protons are so unapt to fuse that even when the tendency is intensified to the full extent of such a device, that still is not enough to allow fusion. At least, that's what I gathered from a lecture I once attended. And nothing but hydrogen is affected, as far as I know. Even in the case of ultrahot protons, the heat produced does not increase without measure. The temperature cools with distance from the intensifier beam, so that only a limited amount of fusion can be forced. Enough to destroy the ship, of course, but there's no question of blowing up the hydrogen-rich oceans, for instance, even if part of the ocean were ultraheated - and certainly not if it were cold."
"But - if the machine gets turned on accidentally in the storage room - "
"I don't think it can get turned on." D.G. opened his hand and in it rested a two - centimeter cube of polished metal. "From what little I - know of such things, this is an activator and the nuclear intensifier can do nothing without it."