Heinrich smiled. "You will never learn that from me—and you should remember that your conduits are laid only seven inches below the surface of the street; it was hardly a man-sized job." He smiled again, and continued. "Neither Mrs. Whitney nor I wished to take anyone wholly into our confidence. She was a perfect assistant; she knew the antecedents of nearly everyone in society here, and she invariably found out, or got others to find out, the motives which inspired strangers to come to Washington. Her husband never interfered with our plans, as he spent most of his time, both day and night, in his studio. The servants never came down in this sub-cellar, and with Mrs. Whitney's connivance, I frequently managed to keep the limousine in the repair shop—and my time was my own. My surroundings were ideal, even the location of this house favored my plans …"
"Until you grew too ambitious," added Connor softly.
"Perhaps." Heinrich gnawed at his underlip as he shot a glance full of venom at Kathleen who stood with head averted, drinking in all that was said. To hurt her, to lower her pride appealed to Heinrich; his silence would not benefit the dead woman, while speech would cruelly hurt and mortify both Kathleen and her father. "My government was anxious to secure Mr. Whitney's inventions; he would not sell to them, although Baron—" he stopped and scowled at Miller—"offered him a large sum. Whitney stuck to it that none but his own country could have the inventions. Then I suggested to Mrs. Whitney that she get the drawings and specifications for me; and again I paid her a large sum of money. But it was as difficult for Mrs. Whitney to get into the studio as for me, and the danger to herself was not small. Her husband was very suspicious, and he never permitted her to remain in the room alone.
"However, because she was not aware I had perfected, as I thought, another plan to secure the invention, and tempted by the sum of money I held before her to succeed, she made another attempt last night. She cried out with disappointment when, after entering, she found only blank paper, and Whitney heard her." He stared at the horrified faces about him, and clearing his voice, added, "The shock finished Whitney."
"You are the devil incarnate!" exclaimed Miss Kiametia, wrathfully.
"I'm not, but he is." Heinrich raised his manacled hands menacingly toward Miller. "I never fully trusted you, von Mueller; although I never found any evidence of your double dealing in your room. But while outwardly appearing to confide in you, I took the precaution to incriminate you should my plans miscarry. I observed the peculiar scar on your finger, and conceived the idea of copying your finger tips in wax. With Mrs. Whitney's help, I secured an impression of your finger prints and had it copied in wax. The workman, another German sympathizer, achieved a wonderful copy of the original, and by my advice Mrs. Whitney wore the wax finger tips whenever she had work to do."
"An ingenious plan, very," ejaculated Mitchell, "and one new to me."
"Mrs. Whitney was wearing them on the night that Sinclair Spencer took it into his besotted brain to investigate this house," went on Heinrich. "Mrs. Whitney told me afterwards that she was on the way here to see me, when she spied Spencer crouching in the elevator, the door of which was open. She was afraid of being discovered if she went upstairs again, and to stay was equally dangerous.
"She had with her a hypodermic syringe which I had given her to use in an emergency." Kathleen straightened up, and for the first time stared full at the spy. "The syringe was filled with a solution of cyanide of potassium," continued Henry. "Adjusting the needle, Mrs. Whitney entered the elevator, and before Spencer could move, thrust it into his neck. Spencer gave one convulsive start, attempted to get up, and his heavy body lurched full against her. She held a knife in her left hand, and as he half arose from his knees, the force of contact against the worn edges of the knife gashed his throat. I had asked Mrs. Whitney to bring me one of the knives which her daughter had for modeling, as I wanted to use some putty down here.
"With great presence of mind," continued Heinrich, after a brief pause which no one cared to break, "Mrs. Whitney ran the elevator to the attic, and before leaving dipped her wax finger tip in the blood flowing from Spencer's throat, and made a distinct impression of von Mueller's finger print on Spencer's white shirt front. Mrs. Whitney left the elevator at the attic, but Detective Mitchell arrived before she missed the syringe. On discovering Miss Grey had it, she made various attempts to get it back.