"That's rather hard to say," Hatch declared thoughtfully. "But I think I should either have gone before anybody else did, through fear of discovery, or else I should have been one of the last, through excess of caution."
"Then proceed along those lines," instructed The Thinking Machine. "You might almost put that down as a law of criminology. It will enable you in the beginning, therefore, to narrow down the dozen or so guests to the first and last who left."
Deeply pondering this little interjection of psychology into a very material affair, Hatch went his way. In the course of events he saw Mrs. Dillingham, who, out of consideration for her guests, flatly refused to give their names.
Luckily for Hatch, the butler didn't feel that way about it at all. This was due partly to the fact that Detective Mallory had given him a miserable half-hour, and partly, perhaps, to the fact that the reporter oiled his greedy palm with a bill of two figures.
"To begin with," said the reporter, "I want to know the names of the first dozen or so persons who arrived here that evening-I mean those who were here when you went up to speak with Mrs. Dillingham."
"I might find out, sir. Their cards were laid on the salver as they arrived, and that salver, I think, has remained undisturbed. Therefore, the first dozen cards on it would give you the names you want."
"Now, that's something like," commented the reporter enthusiastically. "And do you remember any person who left the house rather early that evening?"
"No, sir," was the reply. Then suddenly there came a flash of remembrance across the stoical face. "But I remember that one gentleman arrived here twice. It was this way. Mr. Hawes Campbell came in about eleven o'clock, and passed by without handing me a card. Then I remembered that he had been here earlier and that I had his card. But I don't recall that anyone went out, and I was at the door all evening except when I was up stairs talking to Mrs. Dillingham."
On a bare chance, Hatch went to find Campbell. Inquiry at his two clubs failed to find him, and finally Hatch called at his home.
At the end of five minutes, perhaps, Hatch caught the swish of skirts in the hallway, then the portieres were thrust aside, and-again he was face to face with the mysterious woman of the automobile.
"My brother isn't here," she said calmly, without the slightest sign of recognition. "Can I do anything for you?"
Her brother! Then she was Miss Campbell, and Mrs. Dillingham had called her Dora-Dora Campbell!
"Well-er--" Hatch faltered a little, "it was a personal matter I wanted to see him about."
"I don't know when he will return," Miss Campbell announced.
Hatch stared at her for a moment; he was making up his mind. At last he took the bit in his teeth. "We understand, Miss Campbell," he said at last slowly and emphatically, "that your brother, Hawes Campbell has some information which might be of value in unraveling the mystery surrounding the theft of Mrs. Dillingham's necklace."
Miss Campbell dropped into a chair, and unconsciously Hatch assumed the defensive. "Mrs. Dillingham is very much annoyed, as you must know," Miss Campbell said, "about the publicity given to this affair; particularly as she is confident that the necklace will be returned within a short time. Her only annoyance, beyond the wide publicity, as I said, is that it has not already been returned."
"Returned?" gasped Hatch.
Miss Campbell shrugged her shoulders. "She knows," she continued, "that the necklace is now in safe hands, that there is no danger of its being lost to her; but the situation is such that she cannot demand its return."
"Mrs. Dillingham knows where the necklace is, then?" he asked.
"Yes," replied Miss Campbell.
"Perhaps you know?"
"Perhaps I do," she responded readily. "I can assure you that Mrs. Dillingham is going to take the affair out of the hands of the police, because she knows her property is safe-as safe as if it was in your hands, for instance. It is only a question of time when it will be returned."
"Where is the necklace?" Hatch demanded suddenly.
Again Miss Campbell shrugged her shoulders.
"And what does your brother know about the affair?"
"I can't answer that question, of course," was the response.
"Well, why did he go to Mrs. Dillingham's early in the evening, then go away, and return about eleven o'clock?" insisted the reporter bluntly.
For the first time there came a change in Miss Campbell's manner, a subtle, indefinable something which the reporter readily saw but to which he could attach no meaning.
"I can't say more than I have said," she replied after a moment. "Believe me," and there was a note of earnestness in her voice, "it would be far better for you to drop the matter, because otherwise you may be placed in-in a ridiculous position."
And that was all-a threat, delicately veiled it is true, but a threat nevertheless. She arose and led the way to the door.
Hatch didn't realize the significance of that remark then, nor did it occur to him that the mysterious affair in the automobile had not been mentioned between them; for here was material, knotty, incoherent, inexplicable material, for The Thinking Machine, and there he took it. Again he told the story; but this time all of it-every incident from the moment he hailed the automobile in front of his office on the night of the robbery until Miss Campbell closed the door.
"Why didn't you tell me all of it before?" demanded The Thinking Machine irritably.
"I couldn't see that the affair in the automobile had any connection with the robbery," explained the reporter.
"Couldn't see!" stormed the eminent man of science. "Couldn't see! Every trivial happening on this whole round earth bears on every other happening, no matter how vast or how disconnected it may seem; the correlation of facts makes a perpetually unbroken chain. In other words, if Mrs. Leary hadn't kept a cow, Chicago would not have been destroyed by fire. Couldn't see!"
For an instant The Thinking Machine glared at him; and the change from petulant annoyance to deep abstraction, as that singular brain turned to the problem in hand, was almost visible. It was uncanny. Then the scientist dropped back into his chair with eyes turned upward, and long slender fingers pressed tip to tip. Ten minutes passed, twenty, thirty, and he turned suddenly to the reporter.
"What was the number of that automobile?" he demanded.
Hatch grinned in sheer triumph. Of all the questions he could have anticipated this was the most unlikely, and yet he had the number set down in his note book where it would ultimately become a voucher in his expense account. He consulted the book.
"Number 869019," he replied.
"Now, find that automobile," directed The Thinking Machine. "It is important that you do so at once."
"You mean that the necklace--" Hatch began breathlessly.
"When you bring the automobile here, I will produce the necklace," declared The Thinking Machine emphatically.
Hatch returned half a dozen hours later with troubled lines in his face.
"Automobile No. 869019 has disappeared, evaporated into air," he declared with some heat. "There was one that night, because I was in it, and the highway commission's records show a private cab license granted to John Kilrain under the number; but it has disappeared."
"Where is Kilrain?" inquired The Thinking Machine.
"I didn't see him; but I saw his wife," explained the reporter. "She didn't know anything about automobile No. 869019, or said she didn't. She said his auto car was--"
"No. 610698," interrupted The Thinking Machine. It was not a question; it was the statement as of one who knew.
Hatch stared from the scientist to the note book where he had written down the number the woman gave him, and then he looked his utter astonishment.
"Of course, that is the number," continued The Thinking Machine, as if some one had disputed it. "It is past midnight now, and we won't try to find it; but I'll have it here to-morrow at noon. We shall see for ourselves how safely the necklace has been kept."
Detective Mallory entered and glanced about inquiringly. He saw only The Thinking Machine and Hutchinson Hatch.
"I sent for you," explained the scientist, "because in half an hour or so I shall either place the Dillingham necklace in your hands, or turn over to you the man who knows where it is. You may use your own discretion as to whether or not you will prosecute. Under all the circumstances, I believe the case is one for a sanatorium, rather than prison. In other words, the person who took the necklace is not wholly responsible."