“Then — what poison? A knowledge of botany aided me. I recognized faintly the trace of an odour of an herb which is not only indigenous to, but grows exclusively in Japan. Thus a Japanese poison. Analysis later in my laboratory proved it was a Japanese poison, virulent, and necessarily slow to act unless it is placed directly in an artery. The poison on the court plaster and that you took from Osaka are identical.”
The scientist uncorked the bottle and permitted a single drop of a green liquid to fall on his handkerchief. He allowed a minute or more for evaporation then handed it to Detective Mallory who sniffed at it from a respectful distance. Then The Thinking Machine produced the bit of court plaster he had taken from the dead man’s arm, and again the detective sniffed.
“The same,” t
