'Oh, I almost forgot--here's a letter for you.' 'Where--' 'It came in the Maxineffs' mail this morning. Mrs. Max suggested my bringing it to you.' Noakes took the long, foreign-stamped envelope. The typed superscription was noncommittal, but at the Berlin postmark his eyes narrowed and the knuckles of the hand by his side whitened. He drew a quick breath and looked keenly at the girl. 'Was Mr. Maxineff at home this morning?' he asked quietly. 'No; I believe he is in the city.' 'Oh!' he breathed. 'Thank you very much.' He slipped the letter into his pocket. 'Well, I can't stay any longer.' Noakes pressed her hand. 'And, Cagliostro, when the puzzle's solved, come to see me. I'll sing away the worries, Good-bye.' 'Good-bye, Miss Becky. Excuse my untractableness, won't you?' With a pat to her hat and a smile to Noakes, she was gone. He watched her a moment, then strode rapidly to the stand. Looking through the faint haze, he saw her pass down the straight path which led to the great gate of the Maxineff work-yard. When she was close to it he grasped the switch-lever with cramped fingers. His face was colorless. He moved the lever forward with a jerk, and lifting his eyes, saw her pass out of the gate. Beyond reach of time he waited. Evenly, insistently, a dull brown suffused the mass. Still he waited, fearfully wondering at the stability of this new thing. It kept its even coloring. He pushed back the lever, watched again, and waited. He was afire with joy. He had succeeded; he had created a thing new to the world, an explosive which would be more powerful than the deadliest in existence; he had perfected the work of a week's exquisite danger; he had won. 'I am glad, glad!' he said faintly. As he straightened up he found himself suddenly weak. The strain had been galling, and the madness of gratification consumed his strength. He moved toward the door, stepping very gently, for he knew not how slight a vibration might shatter the delicate affinity in his discovery. He remembered the foreign letter, and taking it from his pocket, tore open the envelope. He looked through the open door, conscious for the first time of the perfectness of the day. It was good to be alive, he thought, free, something accomplished, with leave to tell a girl-- A tall man entered the gate and took the walk toward the laboratory. Noakes looked at him in a moment of amazement, almost of stupefaction. The necessity of instant action startled him to movement. As quickly as he thought, he pushed the door three-quarters shut, replaced the jars from which he had taken his materials, filled a second crucible with a harmless haphazard mixture, and placed it over a dead furnace in a stand in the corner behind the door. He lifted the window-sash. With all his strength he hurled his priceless crucible. By a marvel of speed he had the sash lowered, and was behind the door, when the building was shaken by an explosion.