“But, Field, this woman is hopelessly demented.  There is nothing that can be done for her.  She must be returned to the institution.  I want to keep the knowledge of her identity from Mahr’s son.  Why poison the whole of his young life; why wreck his trust in his father?  Convince yourself in every way, Mr. Field, but the part of mercy is a conspiracy of silence.  Let it be known that an escaped lunatic did the killing—­a certain unknown Mrs. Welles—­and let Brencherly give the reporters all they want.  For them it’s a good story, anyway—­such facts as these, for instance:  he happened by in time to see an attack upon another woman on a bench opposite Mahr’s house, and to hear her boast of her acts.  But I ask as a personal favor that the scandal be avoided.  Brencherly, tell what happened.”

The detective looked up.  “There was an old story—­our office had had it—­that Mahr was a bigamist.  In searching for a motive for the crime, I hit on that.  I had all our data on the subject sent up to me.  I found that our informant stated that Mahr had a wife in an asylum somewhere.  That gave me a suspicion.  I found from headquarters that there were two escapes reported, and one was a woman.  She had broken out of a private institution in Ottawa.  I got word from there that her bills had been paid by a lawyer here—­Twickenbaur.  I already knew that he was Mr. Mahr’s confidential lawyer.  But all this I looked up later, after I’d found the woman.  You see, Mr. Gard is employing me on another matter, and after he returned from Washington, I gave my report to him here.

“Then I went over to Mahr’s house.  I had a curiosity to go over the ground.  It was quite late at night, and I was standing in the dark, looking over the location of the windows, when I saw a woman acting strangely.  She was threatening and talking loudly, crying out that she had a right to kill him.  I sneaked up behind just in time to stop her attack on another woman who was seated on the same bench, and who seemed too ill to defend herself.  Well, sir, I had to give her three hypos before I could take her along.  Then I got her to my rooms, and when she came around, she told me the story.  Of course, sir, you mustn’t expect any coherent narrative, though she is circumstantial enough.  Then I brought over the butler, and he identified her at once.  Mr. Gard advised me not to notify the police until he had seen you.  We got the doctor from the asylum here as quickly as possible.  He’s with her in there now.”

The attorney sat silent a moment, nodding his head slowly.  “I’ll see her, Gard,” he said at length.  “This is a strange story,” he added, as Brencherly disappeared into the anteroom.

Field’s eyes rested on Gard’s face with keen questioning, but he said nothing, for the door opened, admitting the black-clad figure of a middle-aged woman, escorted by a trained nurse and a heavily built man of professional aspect.

“This is—­” Field asked, as his glance took in every detail of the woman’s appearance.