“Our first difficulty is this. We must prove motive. Now, I do not think it will be so very hard to show that this Brotherson cherished feelings of revenge towards Miss Challoner. But I have to acknowledge right here and now that the most skillful and vigourous pumping of the janitor and such other tenants of the Hicks Street tenement as I have dared to approach, fails to show that he has ever held any communication with Mrs. Spotts, or even knew of her existence until her remarkable death attracted his attention. I have spent all the afternoon over this, and with no result. A complete break in the chain at the very start.”

“Humph! we will set that down, then, as so much against us.”

“The next, and this is a bitter pill too, is the almost insurmountable difficulty already recognised of determining how a man, without approaching his victim, could manage to inflict a mortal stab in her breast. No cloak of complete invisibility has yet been found, even by the cleverest criminals.”

“True. The problem is such as a nightmare offers. For years my dreams have been haunted by a gnome who proposes just such puzzles.”

“But there’s an answer to everything, and I’m sure there’s an answer to this. Remember his business. He’s an inventor, with startling ideas. So much I’ve seen for myself. You may stretch probabilities a little in his case; and with this conceded, we may add by way of off-set to the difficulties you mention, coincidences of time and circumstance, and his villainous heart. Oh, I know that I am prejudiced; but wait and see! Miss Challoner was well rid of him even at the cost of her life.”

“She loved him. Even her father believes that now. Some lately discovered letters have come to light to prove that she was by no means so heart free as he supposed. One of her friends, it seems, has also confided to him that once, while she and Miss Challoner were sitting together, she caught Miss Challoner in the act of scribbling capitals over a sheet of paper. They were all B’s with the exception of here and there a neatly turned O, and when her friend twitted her with her fondness for these two letters, and suggested a pleasing monogram, Miss Challoner answered, ‘O. B. (transferring the letters, as you see) are the initials of the finest man in the world.’”

“Gosh! has he heard this story?”

“Who?”

“The gentleman in question.”

“Mr. Brotherson?”

“Yes.”

“I don’t think so. It was told me in confidence.”

“Told you, Mr. Gryce? Pardon my curiosity.”

“By Mr. Challoner.”

“Oh! by Mr. Challoner.”

“He is greatly distressed at having the disgraceful suggestion of suicide attached to his daughter’s name. Notwithstanding the circumstances,—notwithstanding his full recognition of her secret predilection for a man of whom he had never heard till the night of her death, he cannot believe that she struck the blow she did, intentionally. He sent for me in order to inquire if anything could be done to reinstate her in public opinion. He dared not insist that another had wielded the weapon which laid her low so suddenly, but he asked if, in my experience, it had never been known that a woman, hyper-sensitive to some strong man’s magnetic influence, should so follow his thought as to commit an act which never could have arisen in her own mind, uninfluenced. He evidently does not like Brotherson either.”

“And what—what did you—say?” asked Sweetwater, with a halting utterance and his face full of thought.

“I simply quoted the latest authority on hypnotism that no person even in hypnotic sleep could be influenced by another to do what was antagonistic to his natural instincts.”

“Latest authority. That doesn’t mean a final one. Supposing that it was hypnotism! But that wouldn’t account for Mrs. Spotts’ death. Her wound certainly was not a self-inflicted one.”

“How can you be sure?”

“There was no weapon found in the room, or in the court. The snow was searched and the children too. No weapon, Mr. Gryce, not even a paper-cutter. Besides—but how did Mr. Challoner take what you said? Was he satisfied with this assurance?”

“He had to be. I didn’t dare to hold out any hope based on so unsubstantial a theory. But the interview had this effect upon me. If the possibility remains of fixing guilt elsewhere than on Miss Challoner’s inconsiderate impulse, I am ready to devote any amount of time and strength to the work. To see this grieving father relieved from the worst part of his burden is worth some effort and now you know why I have listened so eagerly to you. Sweetwater, I will go with you to the Superintendent. We may not gain his attention and again we may. If we don’t—but we won’t cross that bridge prematurely. When will you be ready for this business?”

“I must be at Headquarters to-morrow.”

“Good, then let it be to-morrow. A taxicab, Sweetwater. The subway for the young. I can no longer manage the stairs.”