His now distraught mind quickly ran the gamut of possibilities. A baffling, indeterminate impression seized him that somebody, somewhere, was reaching out to him through the midnight silence, trying to come in touch with him and speak to him. He looked at the motionless clapper of his transmitter signal-bell, where he had discreetly muffled the little gong with a linen handkerchief. It could not have been the telephone. Yet he caught up the receiver with a gesture of half-angered impatience. “. . . in this house—send an officer at once!” were the words that sped along the wire to his listening ear. An officer at once! Six quick strokes of conjecture seemed to form the missing link to his chain of thought. “My God!” he exclaimed in terror, “that means Frank!” There had been a hitch somewhere, and in some way. And that was the Van Schaicks telephoning for the police—yes, decided Durkin, struggling to keep his clearness of head, it would be first to the Sixty-Seventh Street station that they would send for help. He had already learned, or striven to learn, at such work, not only to think and to act, but to essay his second step of thinking while he accomplished his first in action. He rummaged through a suit-case filled with lineman’s tools, and snatched up a nickel badge similar to that worn by inspectors of the Consolidated Gas Company. It was taking odds, in one way, such as he had never before in his career dared to take. But the case, he felt, was desperate. Once off the Avenue he ran the greater part of the way round the block, for he knew that in five minutes, at the outside, the police themselves would be on the scene. And as he ran he let his alert imagination play along the difficulties that walled him in, feeling, in ever-shifting fancy, for the line of least resistance. He mounted the brownstone steps three at a time, and tore at the old-fashioned bell. He pushed his way authoritatively up through a cluster of servants, shivering and chattering and whispering along the hall. At a young woman in a crimson quilted dressing-gown, faced with baby-blue silk, he flashed his foolish little metal shield. She was a resolute-browed, well-poised girl, looking strangely boyish with her tumbled hair thrown loosely to one side. “I’m the plain-clothes man, the detective from the police station!” He looked at her abstractedly, and curtly shifted his revolver from his hip-pocket to his side-pocket. This caused a stir among the servants. “Get those people out of here!” he ordered. The resolute-browed young woman in the dressing-gown scattered them with a movement of the hand, and slipped a key into his fingers. Then she pointed to a doorway. “This thing was half expected, ma’m, at Headquarters,” said Durkin hurriedly, as he fitted the key. “It’s a woman, isn’t it?” The girl with the resolute brow and the tumbled hair could not say.