be of service I shall expect you to call on me. Just now I
hope you will excuse me. I have some letters to get off--and I will
leave you men to discuss Mr. Haynes' theory without being hampered by a
mere woman. Never mind, Harris," she added as Haynes made as if to
escort her to the ladies' writing room.

As Madame Dupres passed down the steps there was no denying that she
made a splendid impression. Haynes watched her with a glance that was
almost ravenous. There could be no doubt of her influence over him.

As she passed through the lobby she paused at the telegraph desk a
moment, then went into the writing room.

"Yes, I think I have an explanation," began Haynes, when she was out of
sight. "I've been trying to figure out what could have killed Delaney.
Of course I can only guess, but I don't think it is such a bad guess."

"What is it?" asked Craig.

"You remember the mercury vapor light?"

Kennedy nodded.

"Mercury vapor lights of that sort are a pretty good source of
ultra-violet rays sometimes," went on Haynes. "Well, doubtless you know
that various plants belonging to different families produce free prussic
acid. They are really cyanogenetic plants. Light and the assimilation
processes depending on light exert a favorable influence on
cyanogenesis. For instance, a mixture of citric acid with a much
smaller amount of potassium nitrite and a trace of bicarbonate of iron,
if exposed to light, will generate hydrocyanic acid. That, I believe, is
what actually happens in some plant tissues. Animals rarely touch such
plants. I believe that such a process might be aided rather than
retarded by ultra-violet rays. What do you think of it?"

Craig was following Dr. Haynes keenly. As for me, I was astounded by his
frankness. I recalled what Kennedy had already said up in Delaney's
apartment, and watched his face covertly.

"Your explanation is plausible," was all that Craig said. "By the way,
have you found out anything about the Baroness?"

"Not a word, yet," replied Haynes unhesitatingly. "She seems to be out
of town."

"And madame--has she any idea where she is?"

Haynes shook his head. "You may rest assured," replied Haynes in a tone
that was meant to carry conviction, "that if we can find out we shall be
only too happy to do so--ourselves."

There was nothing to be gained by further inquiry here, and I could
imagine that Kennedy was burning with anxiety to get at work on his own
line of inquiry at the l