There came then an interval in the conversation that was very significant. It did not seem a real pause, or the silence real silence, for both men continued to think so rapidly and strongly that one almost imagined their thoughts clothed themselves in words in the air of the room. I was more than a little keyed up with the strange excitement of all I had heard, but what stimulated my nerves more than anything else was the obvious fact that the doctor was clearly upon the trail of discovery. In his mind at that moment, I believe, he had already solved the nature of this perplexing psychical problem. His face was like a mask, and he employed the absolute minimum of gesture and words. All his energies were directed inwards, and by those incalculable methods and processes he had mastered with such infinite patience and study, I felt sure he was already in touch with the forces behind these singular phenomena and laying his deep plans for bringing them into the open, and then effectively dealing with them.