Lucky is sent to investigate sabotage into a Council of Science Project, and finds anti-Council sentiment, and a robot, at work.

I think these stories are getting better and better. At least, the parts of the book where Lucky takes center stage are really good. Unfortunately, I don't think Bigman is all that great as a character or sidekick.

I have to agree with Lucky. Bigman needs to learn to solve problems with stuff other than his fists. He was trying to be subtle, thinking he had solved the problem and trying to get the perpetrator to admit it, but he still had a fist fight -and somebody died because of it.

This book is more a mystery than the previous ones. It also contains a robot, and is subject to the Three Laws of Robotics and the various mechanisms that Asimov uses to show how things can still go wrong, even with all those safeguards.

Lucky is sent to Mercury because of complaints regarding sabotage of a project that could bring light through hyperspace, which would have incredible uses for the energy industry. The engineer in charge of the project, Mindes, actually plays a small part, after trying to kill Lucky. I never got a satisfactory explanation of why he would do this, except that he was under a lot of stress. Lucky, used to the low gravity by now, escapes unscathed.

But the mystery isn't very well wrapped in this story. It was obvious to me who was sabotaging the project and why, just not how. The chief scientist in the small scientific settlement, Dr. Pervale, complains about Earth's dependence on imports from other planets, satellites and so on. Of course he would be opposed to another dependence and try to stop it, especially when he is so concerned about the Sirians. Isn't Aurora settled around Sirius? I believe so, which makes this novel fit right in with the other robot stories. Dr. Pervale went to a conference there, and the spacers were very much opposed to his going.

Lucky determines that the apparitions Mindes sometimes sees on the surface is actually a robot, which Dr. Pervale stole from the Sirians. He sneaks out onto the sunward side of Mercury (it was incorrectly thought at the time that Mercury always faced one side to the sun, like our Moon does to Earth). There he discovers a robot, which had almost burned out its positronic circuits, and obeys the Three Laws, usually. With such a damaged brain, the robot has trouble resolving the priority of the laws, and tries to kill Lucky. Fortunately, Lucky is able to smear some black grime on the robot's head, which absorbs more heat, and completes the destruction of the brain, and the robot dies just in time.

There are a few other characters, all with their own agendas, and all of whom are suspects in the sabotage. Dr. Gardoma is friends with Mindes, who they feel might be sabotaging his own work because it is so far behind schedule and appears to be failing. There is Mr. Cook, who looks suspiciously on edge all the time. And then there is the big unlikable guy, Urteil, who is investigating Council of Science wastes of money and resources. Urteil is belligerent and mean, antagonizing Bigman about his size and heritage. Lucky thinks he is just a side note to the sabotage, though, and he is right. It turns out he was blackmailing Cook into giving him inside information to be used against the Council.

When Bigman and Lucky go into the old mine shafts under the scientific outpost, under the assumption that they will find a Sirian presence buried there, Lucky heads for the surface, and Bigman searches around, keeping up the charade. When he finds Urteil there, spying on him, they get to arguing, and a rock-creature extrudes from the wall and pins them down, absorbing their heat -yet another lifeform in our solar system, after the ones found on Mars and Venus. Bigman is smart enough to set his laser to a slow burn and throw it away, which send the creature after the heat, freeing the two men. But Urteil is not thankful, and Bigman is able to challenge him to a fight under normal Mercurian gravity. Bigman is doing well, but when he sends Urteil sailing into the air, the gravity suddenly comes back to Earth-normal, and Urteil falls to the floor, killing him instantly.

Later, Cook is revealed to be the one who pulled the lever to full gravity, but only to get rid of the blackmailer. Lucky exposes Pervale, and the whole mystery is solved. It is all one neat package, well written and fun. But I get impatient with Bigman, and Urteil was such an obvious bad guy that he couldn't possibly be responsible for the sabotage. I wonder how much of the anti-Council sentiment will be followed up in the next book, especially the backlash from killing the Senator's investigator.