He said, "Opportunity next. It is the general opinion that only Mrs. Delmarre had opportunity since only she could approach her husband in actual personal presence.
"Are we sure of that? Suppose someone other than Mrs. Delmarre had made up his or her mind to kill Dr. Delmarre? Would not such a desperate resolution make the discomfort of personal presence secondary? If any of you were set on murder, wouldn't you bear personal presence just long enough to do the job? Couldn't you sneak into the Delmarre mansion - "
Attlebish interposed frigidly. "You are ignorant of the matter, Earthman. Whether we would or would not doesn't matter. The fact is that Dr. Delmarre himself would not allow seeing, I assure you. If anyone came into his personal presence, regardless of how valued and long-standing a friendship there was between them, Dr. Delmarre would order him away and, if necessary, call robots to help with the ejection."
"True," said Baley, "if Dr. Delmarre were aware that personal presence was involved."
"What do you mean by that?" demanded Dr. Thool in surprise, his voice quavering.
"When you treated Mrs. Delmarre at the scene of the murder," replied Baley, looking full at his questioner, "she assumed you were viewing her, until you actually touched her. So she told me and so I believe. I am, myself, accustomed only to seeing. When I arrived at Solaria and met Security Head Gruer, I assumed I was seeing him. When at the end of our interview, Gruer disappeared, I was taken completely by surprise.
"Now assume the reverse. Suppose that for all a man's adult life, he had been viewing only; never seeing anyone, except on rare occasions his wife. Now suppose someone other than his wife walked up to him in personal presence. Would he not automatically assume that it was a matter of viewing, particularly if a robot had been instructed to advise Delmarre that viewing contact was being set up?"
"Not for a minute," said Quemot. "The sameness of background would give it away."
"Maybe, but how many of you are aware of background now? There would be a minute or so, at least, before Dr. Delmarre would grow aware that something was wrong and in that time, his friend, whoever he was, could walk up to him, raise a club, and bring it down."
"Impossible," said Quemot stubbornly.
"I think not," said Baley. "1 think opportunity must be canceled out as absolute proof that Mrs. Delmarre is the murderess. She had opportunity, but so might others."
Baley waited again. He felt perspiration on his forehead, but wiping it away would have made him look weak. He must maintain absolute charge of the proceedings. The person at whom he was aiming must be placed in self-convinced inferiority. It was hard for an Earthman to do that to a Spacer.
Baley looked from face to face and decided that matters were at least progressing satisfactorily. Even Attlebish looked quite humanly concerned.
"And so we come," he said, "to means, and that is the most puzzling factor of all. The weapon with which the murder was committed was never found."
"We know that," said Attlebish. "If it were not for that point, we would have considered the case against Mrs. Delmarre conclusive. We would never have required an investigation."
"Perhaps," said Baley. "Let's analyze the matter of means, then.
There are two possibilities. Either Mrs. Delmarre committed the murder, or someone else did. If Mrs. Delmarre committed the murder, the weapon would have had to remain at the scene of the crime, unless it were removed later. It has been suggested by my partner, Mr. Olivaw of Aurora, who is not present at the moment, that Dr. Thool had the opportunity to remove the weapon. I ask Dr. Thool now, in the presence of all of us, if he did this, if he removed a weapon while examining the unconscious Mrs. Delmarre?"
Dr. Thool was shaking. "No, no. I swear it. I'll abide any questioning. I swear I removed nothing."
Baley said, "Is there anyone who wishes to suggest at this point that Dr. Thool is lying?"
There was a silence, during which Leebig looked at an object outside of Baley's field of vision and muttered something about the time.
Baley said, "The second possibility is that someone else committed the crime and carried the weapon off with him. But if that were so, one must ask why. Carrying the weapon away is an advertisement of the fact that Mrs. Delmarre was not the murderess. If an outsider were the murderer, he would have to be a complete imbecile not to leave the weapon with the corpse to convict Mrs. Delmarre. Either way, then, the weapon - must be there! Yet it was not seen."
Attlebish said, "Do you take us for fools or for blind men?"
"I take you for Solarians," said Baley calmly, "and therefore incapable of recognizing the particular weapon that was left at the scene of the crime as a weapon."
"I don't understand a word," muttered Klorissa in distress.
Even Gladia, who had scarcely moved a muscle during the course of the meeting, was staring at Baley in surprise.
Baley said, "Dead husband and unconscious wife were not the only individuals on the scene. There was also a disorganized robot."
"Well?" said Leebig angrily.
"Isn't it obvious, then, that, in having eliminated the impossible, what remains, however improbable, is the truth. The robot at the scene of the crime was the murder weapon, a murder weapon none of you could recognize by force of your training."
They all talked at once; all but Gladia, who simply stared.
Baley raised his arms. "Hold it. Quiet! Let me explain!" And once again he told the story of the attempt on Gruer's life and the method