With a wave of her hand, as if she might be a feminine Santa Claus, she was gone, leaving the astonished Grace to stare after her. "Life," she thought, "is strange, so very strange, so much mystery!" She closed the door, but did not stir from her place. She was thinking, and they were long, long thoughts. These thoughts were broken in upon by a second knock on the door. No light tap of a sparrow's wing, this knock, but one like the thump of a policeman demanding admittance in the name of the law. Her hand trembled as she gripped the knob. CHAPTER XXIII A PROMISE THAT IS A THREAT The silence in that little gray home out there on the snow-blown prairies lasted for ten long moments. To those who waited time seemed to creep at a snail's pace. Drew Lane, shifting uneasily in his chair, was about to suggest something--he will never know what--when, sudden as before, all thoughts were drawn to the mysterious talking reflector against the wall. The instant a voice broke the silence in that corner, Drew Lane leaped to his feet. Tom Howe, crouching like a cat, remained motionless in his chair. There was something menacing, sinister, altogether terrible about that voice. The words, more spoken than whispered, caused Johnny's blood to freeze in his veins. "Listen, you Hell hounds!" Those were the words. "Listen! You whisper, do you? Well, so do we! You narrow-cast, and you think we can't listen. Well, we can! "Listen!" The voice became more terrible. "You have been on our trail long enough! Public enemies! Bah!" As if choked with words, the voice ceased for a second. Everyone in the room had turned into a statue. Only the cat was unconscious of it all. He purred loudly in his place among the cushions. And the windmill, poor thing of rusty steel, it uttered one more unearthly scream. "Listen!" The voice was hoarse with hate. "We got you, see? Got all of you. You'll never leave that place, see? Not one of you all! Christmas Eve. It's a laugh!" There came a hoarse chuckle that was terrible to hear. "Hang up your stockings! Get 'em up quick! We're coming to fill 'em, and we'll fill 'em right with machine gun slugs! That's how they'll be filled! "Good-night, everyone!" The speaker's voice dropped to a mocking imitation of a radio announcer. "Good-night. And a Merry Christmas to all!" For a full moment the silence in that little parlor, that through the years had witnessed so much of joy and sorrow, was profound. "It's a joke," Spider said hoarsely at last. "It's no joke!" Drew Lane's lips were white. "I know that voice. "I only wish," he said slowly, "that you ladies were out of it. Those fellows have machine guns. If they cut loose, they'll riddle this place." "I'm a detective's daughter." Joyce Mills stood up square shouldered and slim. "And I a slain policeman's widow." Madame LeClare stood up at her side.