"What happened?" he asked.
"She was stabbed," said Dr. Brander again. "When we examined her we found the knife-a long, keen, short-handled stiletto. It was driven in with great force directly under her left arm and penetrated the heart. She must have been dead when she was lifted from the box at the opera. The stiletto remained in the wound and prevented any flow of blood while its position and the short handle caused it to be overlooked when she was lifted into the carriage. We did not find the knife for several minutes after we arrived. It was covered by her arm."
"Did you tell my wife?" asked Mr. Oliver quickly.
"She was present," the physician went on. "She screamed and fainted. Dr. Seaver is attending her. Her condition is-is not very good. Where is your 'phone? I must notify the police."
Mr. Oliver started to ask something else, paused and dropped back in his chair only to rise instantly and rush up the stairs. Knight into whose face there had come a deadly calm stood stone-like while Dr. Brander used the telephone. At last the physician finished.
"The calling of the police means that Eleanor did not kill herself?" asked the young man.
"It was murder," was the positive reply. "She could not have stabbed herself. The knife went straight in, entering here," and he indicated a spot about four inches below his left arm. "You see," he explained, "it took a very long blade to penetrate the heart."
There was dull despair in Knight's eyes. He dropped down at a table with his head on his arms and sat motionless for a long time. He looked up once and asked a question.
"Where is the knife?"
"I have it," replied Dr. Brander. "I shall turn it over to the authorities."
"Now," began The Thinking Machine in his small, irritated voice as Hutchinson Hatch, reporter, stopped talking and leaned back to listen, "all problems are merely sums in addition, when reduced to their primary parts. Therefore this one is simply a matter of putting facts together in order to prove that two and two do not sometimes but always make four."
Professor Augustus S. F. X. Van Dusen, scientist and logician, paused to adjust his head comfortably on the cushion in the big chair, then resumed:
"Your statement of the case, Mr. Hatch, gives me these absolute facts: Eleanor Oliver is dead; she died of a stab wound; a stiletto made this wound; it was in such a position that she could hardly have inflicted it herself; and Sylvester Knight, her fiance, is under arrest. That's all we know isn't it?"
"You forget that she was stabbed while in a box at the opera," the reporter put in, "in the hearing of three or four thousand persons."
"I forget nothing," snapped the scientist. "It does not appear at all that she was stabbed while in that box. It appears merely that she was ill and might have fainted. She might have been stabbed while in the carriage, or even after she was in her room."
Hatch's eyes opened wide at the bare mention of these possibilities.
"The presumption is of course," The Thinking Machine went on a little less aggressively, "that she was stabbed while in the box, but we can't put that down as an absolute fact to work on until we know it. Remember the stiletto was not found until she was in her room."
This gave the reporter something new to think about and he was silent as he considered it. He saw that either of the possibilities suggested by the scientist was tenable, but on the other hand-on the other hand, and there his mind refused to work.
"You have told me that Knight was arrested at the suggestion of Mr. Oliver last night shortly after the police learned of the affair," The Thinking Machine went on, musingly. "Now just what have you or the police learned as to him? How do they connect him with the affair?"
"First the police acted on the general ground of exclusive opportunity," the reporter explained. "Then Knight was arrested. The stiletto used was not an ordinary one. It had a blade of about seven inches and was very slender, but instead of a guard on it there was only a gold band. The handle is a straight, highly polished piece of wood. Around it, below the gold band where the guard should have been, there were threads as if it had been screwed into something."
"Yes, yes, I see," the other interrupted impatiently. "It was intended to be carried hidden in a walking cane, perhaps, and was screwed down with the blade in the stick. Go on."
"Detective Mallory surmised that when he saw the stiletto," the reporter continued, "so after Knight was locked up he searched his rooms for the other part-the lower end-of the cane."
"And he found it, without the stiletto?"
"Yes, that's the chain against. Knight. First, exclusive opportunity, then the stiletto and the finding of the lower end of the cane in his possession."
"Exclusive fiddlesticks!" exclaimed the scientist irritably. "I presume Knight denies that he killed Miss Oliver?"
"Naturally."
"And where is the stiletto that belongs to his cane? Does he attempt to account for it?"
"He doesn't seem to know where it is-in fact he doesn't deny that the stiletto might be his. He merely says he doesn't know."
The Thinking Machine was silent for several minutes.
"Looks bad for him," he remarked at last.
"Thank you," remarked Hatch dryly. It was one of those rare occasions when the scientist saw a problem exactly as he saw it.
"Miss Oliver and Mr. Knight were to be married-when?"
"Three weeks from next Wednesday."
"I suppose Detective Mallory has the stiletto and cane?"
"Yes."
The Thinking Machine arose and found his hat.
"Let's run over to police headquarters," he suggested.
They found Detective Mallory snugly ensconced behind a fat cigar with beatific satisfaction on his face.
"Ah, gentlemen," he remarked graciously-the graciousness of conscious superiority. "We've nailed it to our friend Knight all right."
"How?" inquired The Thinking Machine.
The detective gloated a little-twisted his tongue around the dainty morsel-before he answered.
"I suppose Hatch has told you the grounds of the arrest?" he asked. "Exclusive opportunity and all that? Then you know, too, how I searched Knight's rooms and found the other part of the stiletto cane. Of course that was enough to convict, but early this evening the last link in the chain against him was supplied when Mrs. Oliver made a statement to me."
The detective paused in enjoyment of the curiosity he had aroused.
"Well?" asked The Thinking Machine, at last.
"Mrs. Oliver heard-understand me-heard Knight threaten her daughter only a few minutes before she was found dead."
"Threaten her?" exclaimed Hatch, as he glanced at The Thinking Machine. "By George!"
Detective Mallory tugged at his moustache complacently.
"Mrs. Oliver heard Knight first say something like, 'Please don't. It won't be very long.' Her daughter answered something she couldn't catch after which she heard Knight say positively, 'You mustn't. If you do I shall do something desperate' or something like that. Now as she remembers it the tone was threatening-it must have been raised in anger to be heard above the anvils. Thus the case is complete."
The Thinking Machine and Hatch silently considered this new point.
"Remember this was only three or four minutes before she was found stabbed," the detective went on with conviction. "It all connects up straight from exclusive opportunity to the ownership of the stiletto; from that to the threat and there you are."