“Yes, and she has settled an important point for us.  There was a possibility, of course, that the paper-cutter which you brought to my notice had never gone with her into the mezzanine.  That she, or some other person, had dropped it in passing through the lobby.  But this girl assures me that her mistress did not enter the lobby that night.  That she accompanied her down in the elevator, and saw her step off at the mezzanine.  She can also swear that the cutter was in a book she carried—­the book we found lying on the desk.  The girl remembers distinctly seeing its peculiarly chased handle projecting from its pages.  Could anything be more satisfactory if —­I was going to say, if the young lady had been of the impulsive type and the provocation greater.  But Miss Challoner’s nature was calm, and were it not for these letters—­” here his arm shifted a little—­“I should not be so sure of my jury’s future verdict.  Love—­” he went on, after a moment of silent consideration of a letter he had chosen from those before him, “disturbs the most equable natures.  When it enters as a factor, we can expect anything —­as you know.  And Miss Challoner evidently was much attached to her correspondent, and naturally felt the reproach conveyed in these lines.”

And Dr. Heath read: 

  “Dear Miss Challoner: 

“Only a man of small spirit could endure what I endured from you the other day.  Love such as mine would be respectable in a clod-hopper, and I think that even you will acknowledge that I stand somewhat higher than that.  Though I was silent under your disapprobation, you shall yet have your answer.  It will not lack point because of its necessary delay.”

“A threat!”

The words sprang from Sweetwater, and were evidently involuntary.  Dr. Heath paid no notice, but Mr. Gryce, in shifting his hands on his cane top, gave them a sidelong look which was not without a hint of fresh interest in a case concerning which he had believed himself to have said his last word.

“It is the only letter of them all which conveys anything like a reproach,” proceeded the coroner.  “The rest are ardent enough and, I must acknowledge that, so far as I have allowed myself to look into them, sufficiently respectful.  Her surprise must consequently have been great at receiving these lines, and her resentment equally so.  If the two met afterwards—­But I have not shown you the signature.  To the poor father it conveyed nothing—­some facts have been kept from him—­but to us—­” here he whirled the letter about so that Sweetwater, at least, could see the name, “it conveys a hope that we may yet understand Miss Challoner.”

“Brotherson!” exclaimed the young detective in loud surprise.  “Brotherson!  The man who—­”

“The man who left this building just before or simultaneously with the alarm caused by Miss Challoner’s fall.  It clears away some of the clouds befogging us.  She probably caught sight of him in the lobby, and in the passion of the moment forgot her usual instincts and drove the sharp-pointed weapon into her heart.”