Armstrong was on the point of demurring, but the last sentence reassured him.  He would reveal nothing by it—­yet.

Still the man was trembling like a leaf.  He wrote: 

“Give Whitecap one hundred shocks—­A Victim.”

For a moment Kennedy studied the note carefully.  “Oh—­er—­I forgot, Armstrong, but a few days ago an anonymous letter was sent to Mrs. Sutphen, signed ‘A Friend.’  Do you know anything about it?”

“A note?” the man repeated.  “Mrs. Sutphen?  I don’t know anything about any note, or Mrs. Sutphen either.”

Kennedy was still studying his record.  “This,” he remarked slowly, “is what I call my psychophysical test for falsehood.  Lying, when it is practiced by an expert, is not easily detected by the most careful scrutiny of the liar’s appearance and manner.

“However, successful means have been developed for the detection of falsehood by the study of experimental psychology.  Walter, I think you will recall the test I used once, the psychophysical factor of the character and rapidity of the mental process known as the association of ideas?”

I nodded acquiescence.

“Well,” he resumed, “in criminal jurisprudence, I find an even more simple and more subjective test which has been recently devised.  Professor Stoerring of Bonn has found out that feelings of pleasure and pain produce well-defined changes in respiration.  Similar effects are produced by lying, according to the famous Professor Benussi of Graz.

“These effects are unerring, unequivocal.  The utterance of a false statement increases respiration; of a true statement decreases.  The importance and scope of these discoveries are obvious.”

Craig was figuring rapidly on a piece of paper.  “This is a certain and objective criterion,” he continued as he figured, “between truth and falsehood.  Even when a clever liar endeavors to escape detection by breathing irregularly, it is likely to fail, for Benussi has investigated and found that voluntary changes in respiration don’t alter the result.  You see, the quotient obtained by dividing the time of inspiration by the time of expiration gives me the result.”

He looked up suddenly.  “Armstrong, you are telling the truth about some things—­downright lies about others.  You are a drug fiend—­ but I will be lenient with you, for one reason.  Contrary to everything that I would have expected, you are really trying to save that poor half-witted girl whom you love from the terrible habit that has gripped you.  That is why you held out the quarter of the one hundred tablets.  That is why you wrote the note to Mrs. Sutphen, hoping that she might be treated in some institution.”

Kennedy paused as a look of incredulity passed over Armstrong’s face.

“Another thing you said was true,” added Kennedy.  “You can get all the heroin you want.  Armstrong, you will put the address of that place on the outside of the note, or both you and Whitecap go to jail.  Snowbird will be left to her own devices—­she can get all the ‘snow,’ as some of you fiends call it, that she wants from those who might exploit her.”