Dr. Priestley smiled as the conviction that this was so came back to him with redoubled force. Utterly contrary to his usual methods of procedure, he had formed a theory based entirely upon conjecture. So far, these facts by which it must be tested seemed to point to the incorrectness of this theory. Yet, were they facts? Was it not even yet possible that some master brain had arranged these seeming facts in order purposely to mislead an investigator like himself? And, if so, what unknown dangers might he not be incurring by the attempt to prove them false?

The Professor had never shirked danger throughout the whole course of his career. And in this case, as he reflected, he already stood in such imminent danger that his present actions could hardly increase it. If his theory were correct, a determined and unknown assassin held in his hand already the weapon which was aimed against his life. Why had he not struck, months ago, when the Professor was in blissful ignorance that his life was threatened? This was one of the aspects of a case which, in spite of the perils which it held for himself, thrilled him as no case had ever thrilled him before.