He resumed his seat, smoking hard.

"Fu-Manchu has made the blunder common to all men of unusual genius,"
he said. "He has underrated his adversary. He has not given me credit
for perceiving the meaning of the scented messages. He has thrown away
one powerful weapon--to get such a message into my hands--and he thinks
that once safe within doors, I shall sleep, unsuspecting, and die as
Sir Crichton died. But without the indiscretion of your charming
friend, I should have known what to expect when I receive her
'information'--which by the way, consists of a blank sheet of paper."

"Smith," I broke in, "who is she?"

"She is either Fu-Manchu's daughter, his wife, or his slave. I am
inclined to believe the last, for she has no will but his will,
except"--with a quizzical glance--"in a certain instance."

"How can you jest with some awful thing--Heaven knows what--hanging
over your head? What is the meaning of these perfumed envelopes? How
did Sir Crichton die?"

"He died of the Zayat Kiss. Ask me what that is and I reply 'I do not
know.' The zayats are the Burmese caravanserais, or rest-houses. Along
a certain route--upon which I set eyes, for the first and only time,
upon Dr. Fu-Manchu--travelers who use them sometimes die as Sir
Crichton died, with nothing to show the cause of death but a little
mark upon the neck, face, or limb, which has earned, in those parts,
the title of the 'Zayat Kiss.' The rest-houses along that route are
shunned now. I have my theory and I hope to prove it to-night, if I
live. It will be one more broken weapon in his fiendish armory, and it
is thus, and thus only, that I can hope to crush him. This was my
principal reason for not enlightening Dr. Cleeve. Even walls have ears
where Fu-Manchu is concerned, so I feigned ignorance of the meaning of
the mark, knowing that he would be almost certain to employ the same
methods upon some other victim. I wanted an opportunity to study the
Zayat Kiss in operation, and I shall have one."

"But the scented envelopes?"

"In the swampy forests of the district I have referred to a rare
species of orchid, almost green, and with a peculiar scent, is
sometimes met with. I recognized the heavy perfume at once. I take it
that the thing which kills the traveler is attracted by this orchid.
You will notice that the perfume clings to whatever it touches. I
doubt if it can be washed off in the ordinary way. After at least one
unsuccessful att