"What was she doing?" Geoffrey asked.
"It is an appliance for exhausting air," Tchigorsky explained. "You take a powder and place it on a hot plate. Directly it begins to burn it draws up all the air. The thing has been known in the East for thousands of years. Mrs. May applied electricity to give her greater scope. A plate of the powder was to be heated in the room of everybody in the castle when asleep.
"A few minutes and the thing is done. Then the wires are withdrawn and gradually the different rooms fill with air again. The burnt powder leaves no trace. Then you are all found dead in your beds and nobody knows how it is done. The wires are easily drawn back to the battery and the whole thing is destroyed."
Geoffrey shuddered.
"What a fiend!"
CHAPTER XLVI NEARING THE END
It was some time before any one spoke. Geoffrey was turning the whole matter over in his mind. He was still puzzled.