Before them were three men or what had been three men. All stood in strained attitudes with a look of horror frozen on their faces. The thing that made the spectators shudder was that their bodies had, by some diabolical method, been rendered semi-transparent. The dull red light which suffused the room emanated from the three bodies. Dr. Bird examined them closely, being careful not to touch them. "The identity of my treacherous assistant is known," he said grimly as he pointed at the middle figure. "It was Gerond. What is this?" He took an envelope from the hand of the middle figure and opened it. A sheet of paper fell out and he picked it up and read it. "My dear Mr. Bolton," ran the note. "Your methods of tracing and picketing my headquarters are so crude as to be almost laughable. This base has served its purpose and we were ready to abandon it in any event, but I couldn't resist the temptation to let you almost nab us. The three men whom you will find here are agents who failed in their duty. If you are interested in learning the method of their execution, you might take to heart the words of your colleague, Dr. Bird: 'The clue lies in those windows.'" Carnes glanced at the windows and gave a cry of surprise. The glass was opaque, as had been the glass in the doctor's laboratory and the glass in the infirmary at Atlanta. The fogging however, was much more pronounced, and the opaque glass gave faintly the same red effulgence which came from the three bodies. "What does it mean, Doctor?" he asked. "I don't know, Carnes," said Dr. Bird slowly. "I foresee that I am going to have to do a great deal of work on short wave-lengths soon. It is doubtless the effect of some modification of the black lamp which has done it. Look out!" * * * * * He leaped to one side as he spoke, drawing Bolton and Carnes with him. A panel in the side of the wall opposite the doorway had slid silently open and through the opening poured out a beam of fiery red. Full on the three bodies it fell, and then spread out to fill the room. Dr. Bird had drawn the two nearest men out of the direct beam, but one of the secret service men stood full in its path. In the excitement of entering he had dropped his vitrilene shield and the livid ray fell full on his defenceless body. As they watched an expression of horror spread over his face and he strove to move to one side, but he was held helpless. Slowly he stiffened; and, as the ray bored through him, his body became semi-transparent and the same dull red glow which emanated from the three bodies they had found began to shine forth from him. Bolton strove to break from the doctor's grasp and rush to the rescue but Dr. Bird held him with a grip of iron.