whole lot。 You may imagine with what interest I put the page I
wished to examine under my microscope and laid beside it the piece
of glass which； you will perhaps remember； I cut from a window of
the room in which the murder was committed。 I believe I have never
yet explained to Miss Darrow why I preserved that bit of glass。
There were two reasons for it。 The house had been primed that day
and there were two smutches of paint upon the glass and two almost
identical smutches upon the sill。 One was a sinuous line； as if
the glass had been struck with a short bit of rope； … or possibly
rubber tubing since no rope…like texture was visible； … which had
previously been soiled with the paint from the sill。 The other mark
was that of a human thumb。 I had seen at the World's Fair an exhibit
of these thumbmarks collected by a Frenchman who has made an
exhaustive study of the subject； and had learned there for the first
time that no two thumbs in the world can make the same mark。 I knew；
therefore； that this slip of glass would at any time tell me whether
or not a suspected man were guilty。 I had not failed to get the
thumb…marks of the men who painted the house on that day； as well
as those of every other person known to be about the place。 The
marks upon the glass could not； by any possibility； have been made
by any of them。 The deduction was inevitable。 They were made by
the man who stood by the window when the murder was committed。
〃You will be surprised when I tell you it was some moments before
I could summon up courage to look through my microscope upon the
page beneath it。 You see； I had been seized by an unaccountable
conviction that I had at last found a real clue to the murderer；
and I dreaded lest the first glance should show this to have been
an idle delusion。 At length I looked。 The thumb that had pressed
the paper was the thumb that had pressed the glass！ There was not
a doubt of it。 My suspicions were confirmed。 Everything now
regarding this book was of immense importance。 The page upon which
the mark was found … well； I think you would open your eyes if I
were to read it to you。 I will defer this pleasure； however； till
I see if my suspicions are correct。 The thumb…mark is upon page
469 of 'Poisons； Their Effects and Detection；' by Alexander Wynter
Blyth。
〃No sooner had I made sure of my discovery than I set out for No。 5
Oak Street； the address given by Rizzi。 There was no such person
there； nor had there been anyone of that name in the house during
the three years of the present tenant's occupancy。 I went to 15
Staniford Place with the same result。 A young woman about
twenty…five years of age came to the door。 She informed me that
she had been born in the house and had always lived there。 She had
never known anyone by the name of Weltz。 This was just what I had
expected。 The man for whom we are searching is shrewd almost beyond
belief； and if we succeed in finding him it will not； we may be
assured； be the result of any bungling on his part。
〃I have now told you all I have learned； or rather all that is
sufficiently definite to communicate … it is not much； yet it is a
clue and may serve to give our hope a new lease of life。 What do
you think of it； Miss Darrow？〃
〃I think what you have learned；〃 Gwen replied； 〃will be of the
utmost importance。 You have now something definite to guide you。
I am most fortunate in having the services of such a detective；
… indeed； I am at a loss to know how to thank you for all you have
done； … for all you are doing； I … 〃
〃My dear Miss Darrow；〃 Maitland interrupted； 〃I need no thanks。 Be
assured I am selfish in all I do。 It is a pleasure to me； therefore
I do it。 You see I deserve no credit。 If I am able to free you
from the danger of sacrificing yourself； I shall be more than
repaid。〃
Gwen made no reply； but I； sitting as I did close beside her； saw
the moisture gather between her drooping lids。 Maitland took his
leave almost immediately； having； he said； a long evening's work
before him； while Gwen； Alice； and I discussed the news he had
brought us； until far into the night。 I did not see him the next
day； which was Tuesday； and I believe not on Wednesday。 It was
Thursday afternoon； if I do not mistake； that he sent me a note
asking me to call on him at his office。 I went at once； thinking
it might be something very important。 I found him alone and
waiting for me。
〃I wanted；〃 he began as soon as I was seated； 〃to talk this matter
over with you。 You see the great difficulty which besets me in this
case is that nearly all our evidence； while it is of a nature to
enable us to convict our man once we have him； is yet of almost no
assistance to us in finding him。 What do we know of him up to date；
or at least of what do we feel reasonably assured？ Let us see。
John Darrow was poisoned in some mysterious way by a man who was
stationed just outside the partly opened window。 The weapon； or
whatever was used as such； was taken away by the murderer。 Nothing
in the nature of a projectile could have been employed； since the
wound was upon a part of the victim's throat known to have been
turned away from the window and to have been completely shielded
upon that side by the high and massive back of the chair in which
the victim sat。
〃He was fully eight feet from the casement； so that the assassin
could not have reached in and struck him。 There were no footprints
by the window； as the assassin had strapped small boards upon his
feet。 It is most likely； therefore； that he has some peculiarity
about his feet which he thought best to conceal。 He is about five
feet five inches tall； weighs about one hundred and thirty…five
pounds； and steps three or four inches longer when the right foot
is thrown forward than he does when the left foot leads。 We have a
cast of the assassin's hand showing unmistakable evidence of the
habit of biting the nails； with the exception of that of the little
finger； which nail； by the way； is abnormally long； and could only
have been spared for some special reason。 The murderer is most
likely a foreigner。 His handwriting would indicate this even if we
did not know； from the books he read； how conversant he is with at
least one foreign tongue。 Again； he has some decided interest in
the subject of cancers and； perhaps； some interest in legerdemain；
if we may judge from his perusal of Robert Houdin's book。
〃There are one or two other things I have learned； but this； so far
as any present effect is concerned； is about all we know； and it
doesn't seem to make the conduct of our search a very easy matter。
We have clearly to deal with a man who is possessed not merely of
low criminal cunning； but； I have reason to believe； with one who
has education and culture； and； if anything can be judged from
handwriting； rare strength of character as well。 If we could only
find some motive！ No one but a maniac would do such a deed without
a motive； yet we can't find one。 A maniac！ By Jove！ I hadn't
thought of that。 What do you think of the idea？ 'Though this be
madness； yet there is method in't；' eh？〃
I told him that the maniac theory did not appeal to me very strongly。
〃Madness； to be sure； is often exceedingly cunning；〃 I said； 〃but
it is hardly capable of such sustained masterfulness as our criminal
has evinced。〃
〃Look here； Doc；〃 Maitland said； breaking out suddenly； 〃I've an
idea。 Might not this fellow's interest in cancers be due to his
having one himself？ Suppose you make a canvass of the specialists
on cancer in Boston and vicinity； and see if any of them remember
being consulted by a patient answering the description with which I
will provide you。 In addition to this I will insert an ad in the
papers calling attention to a new method for the cure of cancer；
and asking all interested to call at your office for further
particulars。 The plan does not promise much； still it may bring
him。 What do you say？〃
I expressed my willingness to do all in my power to aid him； and he
left me。 The next morning's papers contained the advertisement and
I had several calls in answer to it。 These would have caused me
much inconvenience had I not explained the whole ruse in confidence
to a medical friend who made a specialty of the treatment of cancers；
and persuaded him to come to my office during the hours specified
in the advertisement。 When a patient would call I would satisfy
myself that it was neither the person we were searching for； nor
anyone sent by him to make inquiries； and then turn him over to my
colleague； Dr。 Rhodes。 It would never have occurred to me to
interest myself in any patient who did not answer the description
given me by Maitland； had he not especially cautioned me in this
regard。
〃We have；〃 he said； 〃to deal with a man possessed of ability of no
common order。 We have already seen that he never runs a risk；
however slight； which he can avoid。 It is more than likely；
therefore； if our advertisement meets his eye and interests him； he
will inquire into it through some second party。 Again； we are by
no means certain that his interest in cancers is a purely personal
one。 Perhaps it is a wife； a sister； or some other relative who is
afflicted。 In this case we could hardly expect him to come himself。
Let me caution you； therefore； to closely scrutinise all applicants
and question them until you are satisfied they are in nowise
connected with the man for whom we are searching。〃
I followed this advice most carefully and had no difficulty in
convincing myself that none of my callers had any relation whatsoever
with the murderer of John Darrow。 This order of things was
continued for several days with the same result。 In the meantime
Maitland was working upon a new clue he had discovered。 He would
tell me all about it； he said； when he had followed it to the end。
This was on Tuesday。 On Friday he came to the house and informed us
that he had met a man who had known a M。 Henri Cazot； a Frenchman
whose description seemed to tally perfectly with nearly all we knew
of Mr。 Darrow's murderer。
〃It came about in this way；〃 Maitland began in response to