hat knock.
Hasten the time when we may meet, malignant knaves. Never again shall
I avoid you. Henceforth, I go about my business as before, for it is
thus that I may expect the sooner to encounter you."

An urgent matter would require the doctor's presence in the
municipality of Evanston that night. He could not expect to return
before twelve o'clock in the morning and of this informing the cook,
who in the temporary reduction of the family carried on the household
without the aid of a second girl, he departed northward. It was past
the hour of one when he let himself in the front door of his
residence. A pleasant savor of various viands saluted his nostrils and
in the drawing-room he observed that the chairs and tables had all
been thrust against the wall as if to clear the floor for dancing. In
the dining-room, the evidence of recent festivity was complete, for
the table was covered with the remnants of a sumptuous repast. No
words were needed to tell him that Olga Blomgren, the cook, had taken
advantage of the foreknowledge of his absence to entertain a wide
circle of friends; but here indeed was a mystery. Why had she not set
everything in order and removed all traces of the entertainment? He
moved toward the kitchen in wonder and--his heart stood still. The
beams of the lamp held above his head were shot back by the gleam of
blue and white satin, his wife's favorite ball dress on the kitchen
floor. But it was not his wife's fair hair and snowy shoulders that,
rising out of the glistening blue and white, were striped with a
glistening red, but the snowy shoulders and fair hair of poor Olga
Blomgren. Thus had she paid for her hour of magnificence. Thus had
death cut her down because the maid's form was of the same statuesque
beauty as her mistress's. Tenderly the doctor stooped to lift up the
dead girl, stricken in her mistress's stead. There was a poniard in
her throat, and it impaled a piece of paper upon which was written
"Knock."

"Knock, knock--" the next knock would be upon his own heart.

Whatever design the doctor had held of not appealing to the police for
protection against his invisible foes, his affairs had now reached a
point where the intervention of the officers of the law could no
longer be avoided. Poor Jacques could be consigned to earth without
the intervention of priest or police, but the murder of Olga was a
matter for official investigation. With that crafty and subtle way the
astute sleuths