one entered that room. Only she and I work there."

"But when she finished the letters, she went out?" insisted The Thinking Machine.

"No," declared the financier, "she didn't even leave her desk."

"Or perhaps sent something out—carbon copies of the letters?"

"No."

"Or called up a friend on the telephone?" continued The Thinking Machine quietly.

"Nor that," retorted Grayson.

"Or signaled to someone through the window?"

"No," said the financier again. "She finished the letters, then remained quietly at her desk, reading a book. She hardly moved for two hours."

The Thinking Machine lowered his eyes and glared straight into those of the financier. "Someone listened at the window?" he went on after a moment.

"No. It is sixteen stories up, fronting the street, and there is no fire escape."

"Or the door?"

"If you knew the arrangement of my offices, you would see how utterly impossible that would be, because—"

"Nothing is impossible, Mr. Grayson," snapped the scientist abruptly. "It might be improbable, but not impossible. Don't say that—it annoys me exceedingly." He was silent for a moment. Grayson stared at him blankly. "Did either you or she answer a call on the 'phone?"

"No one called; we called no one."

"Any apertures—holes or cracks—in your flooring or walls or ceilings?" demanded the scientist.

"Private detectives whom I had employed looked for such an opening, and there was none," replied Grayson.

Again The Thinking Machine was silent for a long time. Grayson lighted a fresh cigar and settled back in his chair patiently. Faint cobwebby lines began to appear on the dome-like brow of the scientist, and slowly the squint eyes were narrowing.

"The letters you wrote were intercepted?" he suggested at last.

"No," exclaimed Grayson flatly. "Those letters were sent direct to the brokers by a dozen different methods, and every one of them had been delivered by five minutes of ten o'clock, when 'Change begins business. The last one left me at ten minutes of ten."

"Dear me! Dear me!" The Thinking Machine rose and paced the length of the room.

"You don't give me credit for the extraordinary precautions I have taken, particularly in this last P., Q. & X. deal," Grayson continued. "I left positively nothing undone to insure absolute secrecy. And Miss Winthrop, I know, is innocent of any connection with the affair. The private detectives suspected her at first, as you do, and she was watched in and out of my office for weeks. When she was not under my eyes, she was under the eyes of men to whom I had promised an extravagant sum of money if they found the leak. She didn't know it then, and doesn't know it now. I am heartily ashamed of it all, because the investigation proved her absolute loyalty to me. On this last day she was directly under my eyes for two hours; and she didn't make one movement that I didn't note, because the thing meant millions to me. That proved beyond all question that it was no fault of hers. What could I do?"

The Thinking Machine didn't say. He paused at a window, and for minute after minute stood motionless there, with eyes narrowed to mere slits.

"I was on the point of discharging Miss Winthrop," the financier went on, "but her innocence was so thoroughly proved to me by this last affair that it would have been unjust, and so——"

Suddenly the scientist turned upon his visitor. "Do you talk in your sleep?" he demanded.

"No," was the prompt reply. "I had thought of that too. It is beyond all ordinary things, Professor. Yet there is a leak that is costing me millions."

"It comes down to this, Mr. Grayson," The Thinking Machine informed him crabbedly. "If only you and Miss Winthrop knew those plans, and no one else, and they did leak, and were not deduced from other things, then either you or she permitted them to leak, intentionally or unintentionally. That is as pure logic as two and two make four; there is no need