"However, she was the active spirit; hers was the hand that held the weapon, while the more timid man waited at his desk in the adjoining room. There she paused in her flight, and told him the deed had been committed; and there he waited until about a quarter-past five, when, moved by that irresistible impulse which leads some murderers to gloat over their handiwork, he crossed the hall and looked upon the dead man. This happened while Lynden was on his way to headquarters with the news of the murder. Fairchild's actions were so singular that they attracted both Doctor Westbrook's and Howe's attention. Overcome with horror, he turned and fled without a word. That is the last seen of Clay Fairchild, and that is why I sent a note to Barton and Adams, who were waiting below, to find him.
"Under this theory I can as yet conjecture but a single motive—Fairchild's interest in the woman; and as to what hers is, we must wait until her identity is established."
Converse paused. His eyes narrowed, and he ran the tip of his tongue across his lips with a deliberate lateral movement.
"I'd like very much to lay my hand on that fair lady," said he, presently, in a quiet manner; but an observer might have remarked that a shudder convulsed the corpulent figure of Mr. Merkel, and that Mr. Mountjoy shot at him a quick, keen look, and then nodded his head in silent approval.
The Captain went on at once.
"There is one incongruous element in this theory, however. When the blow was struck the deceased was in the act of turning toward Doctor Westbrook's door, and consequently his back was almost squarely presented to Mr. Nettleton's. The wound, as you know, is not only on the left side of the throat, but tends backward toward the spinal column, which the point of the blade penetrated. Suspended from the centre of the hall, and on a line with the centre of the two doorways, is an electric light. Now, then, the murderer coming from behind the victim could, under the present circumstances, strike the blow in one of two ways: it was either a left-handed person, or, if right-handed, the murderer must have stepped to deceased's left, and a little in front of him, facing in the same direction, and struck to the right and backward. If the latter theory is correct, the murderer would have been between De Sanchez and the hall window opening into the light-well, and so close to the window that he—or she, if it was a woman—would have been not only plainly visible from the windows on the opposite side of the light-well, but would have cast a distinct shadow because of the electric light. If the murderer was left-handed he would not have been obliged to go so far to De Sanchez's left, and consequently would have remained so nearly beneath the electric light that the only shadow would have been on the hall floor.
"Now, from the point where Judge Petty was looking into the light-well, one cannot quite see Doctor Westbrook's door through the Nettleton hall window; but the hall window would be so far within such a person's range of vision that the slightest obscuring of the light would attract notice. Judge Petty recollects that the light was burning at five o'clock yesterday evening, and he is positive that there was no shadow at the hall window, and that no one approached close to it while he was looking into the light-well.
"Now mark this—at least, as a singular coincidence—while Doctor Westbrook is not what you might call left-handed, he can use both hands equally well."
"Ambidextrous," suggested Mr. Mountjoy.
Converse nodded. "Exactly," said he; "ambidextrous." He continued: