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to myself； have suggested to your father's assassin the course he pursued。
I concluded to go to the library and ask for a list of the names of persons
who had taken out this book for a few months prior to your father's death。
I was fully aware that the chance of my learning anything in this way was
very slight； In the first place； I reasoned that it was not especially likely
your father's murderer had read 'The Sign of the Four；' and； in the second
place； even if he had； what assurance had I that he had read this particular
copy of it？ Notwithstanding this； however； I felt impelled to give my
synthetical theory a fair experimental trial。 I was informed by the
Library attendants that the book had been much read； and given the list of
some twenty names of persons who had borrowed the book during the
time I had specified。 With these twenty…odd names before me； I sat down
to think what my next step should be。 I went carefully over this chain of
reasoning link by link。 'I wish to find a certain murderer； and have
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The Darrow Enigma
adopted this method in the hope that it may help me。 If I derive any
assistance at all from it； it will be because my man has read this particular
copy of this work； therefore； I may as well assume at the start that among
these twenty…odd names is that of the man I want。 Is there any possibility
of this crime having been committed by a woman？' was my next question；
and my answer was； 'Yes； a possibility； but it is so decidedly improbable
that I may count it out for the time being。' Accordingly； I set aside all the
female names； which cut my list down to eighteen。 Several of the
applicants had only signed the initials of their given names； and the
attendant； copying them from the slips； had done likewise； so I was
obliged to go to the registration clerk to determine this question of sex；
and； while there； I also ascertained the age of each applicant … that is； of all
but two。 The registrar could give me no information regarding J。 Z。
Weltz； or B。 W。 Rizzi。 When I told him that one of the clerks had copied
the names for me from application slips； he informed me that if I would go
back to her I would undoubtedly find she had taken the two last…mentioned
names from the green slips used in applying for books for hall use； as
neither J。 Z。 Weltz nor B。 W。 Rizzi was a card…holder。
〃I decided to let these two names rest a while； and to give my attention
to the others。 After careful deliberation I felt reasonably sure your
father's assassin could not fail to be a man of mature judgment and
extraordinary cunning； probably a man past middle life … at all events； I
could safely say he was over twenty…one years of age。 Proceeding upon
this assumption my list was reduced to ten names。 But how should I
further continue this process of exclusion？ This was the question which
now confronted me。 I could think of but one way； apart from personally
making the gentlemen's acquaintance； which I did not then wish to do； and
that was to ascertain what other books they had borrowed immediately
before and after they had read 'The Sign of the Four。' This was the
course I determined to pursue。
〃If you ask me why I so persistently followed an investigation； a
successful outcome of which anyone must recognise would be little short
of miraculous； I can only say that I felt impelled to do so。 Perhaps the
impulse was due to my habit of testing patiently and thoroughly each new
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The Darrow Enigma
theory which impresses me as having any degree of probability； and
perhaps it was due to something else … Cleopatra； perhaps； eh； Doctor？ … I
don't know。 I determined； however； to thoroughly satisfy myself
regarding these ten men。 I made a careful list； with the assistance of an
attendant； of ten books taken by each man； five taken just prior to 'The
Sign of the Four；' and the other five just following it。 I made no
deductions until the list was completed； although I began to see certain
things of interest as we worked upon it。 At length the whole hundred
titles were spread before me； and I sat down to see what I could make of
them。 I purposely reserved consideration of the books borrowed by
Weltz and Rizzi until the last； because I had been able to learn nothing of
them； and considered； therefore； that they were the most difficult persons
in the list about whom to satisfy myself。 I found the other eight exhibited
no system in their reading。 One had read … I think I can remember the
books in the order in which they were borrowed … 'Thelma；' 'Under Two
Flags；' 'David Copperfield；' 'The Story of an African Farm；' 'A Study in
Scarlet；' 'The Sign of the Four；' 'The Prisoner of Zenda；' 'The Dolly
Dialogues；' 'The Yellow Aster；' 'The Superfluous Woman；' and 'Ideala。'
This is a fair sample of the other seven。 Not so； however； with Messrs。
Weltz and Rizzi。 The reading of these men at once impressed me as having
a purpose behind it。
〃I will read you a list of the books taken by Weltz and Rizzi； just to see
what you will make out of it：
WELTZ RIZZI
I。〃Lecons de Toxicologic；〃 1。〃Traite de Toxicologic；〃 par M。
Orifia。 par C。 P。 Galtier。
2。〃The Poisons of Asps and 2。〃The Poisons of Asps and Other
Stories；〃 by Florence Other Stories；〃 by Florence Marryat。
Marryat。
3。〃A Practical Essay on3。〃A Practical Essay on Cancer；〃 by C。 T。
Johnson。 Cancer；〃 by C。 T。 Johnson。
4。〃The Sharper Detected4。〃The Sharper Detected and Exposed；〃
by R。 Houdin。 and Exposed；〃 by R。 Houdin。
5。〃The Sign of the Four；〃 5。〃The Sign of the Four；〃 by A。
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The Darrow Enigma
Conan Doyle。 by A。 Conan Doyle。
6。〃Cancer； a New Method of 6。〃Legal Chemistry： A
Treatment；〃 by W。 H。 Guide to the Detection of Broadbent。
Poisons； Examinations of Stains； etc。； as Applied to=20
Chemical Jurisprudence。〃 From the French of A。 Naquet=20 by
J。 P。 Battershall； Nat。Sc。D。
7。〃Reports of Trials for 7。〃Traite Pratique des =20 Murder by
Poisoning；〃Maladies Cancerences；〃 by G。 L。 Browne and C。 par H。
Lebert。 G。Stewart。 =20
8。〃A Practical Treatise on 8。〃A Practical Treatise on Poisons；〃 by 0。
H。 Costill。 Poisons；〃 by 0。 H。 Costill。
9。〃Poisons； Their Effects 9。〃A Treatise on Poisons in and
Detection；〃 by Alexander Relation to Medical=20 Wynter Blyth。
Jurisprudence； Physiology； and the Practice of Physic；〃=20 by
R。 Christison；M。D。； F。R。S。E。
10。〃Poisons； Their Effects 10。〃Poisons； Their Effects and
Detection；〃 by Alexander and Detection；〃 by Alexander =20 Wynter
Blyth。 Wynter Blyth。
〃There； do you wonder that the perusal of that list excited me？ Come；
now； before I go any further； tell me what you make of it； Doc；〃 and he
passed it to me。
〃There seems to me to be a singular unanimity of purpose existing
between these two men；〃 I said； 〃not only as regards the subject…matter of
their reading； but in no less than six cases they have both perused the same
volume。 This never happened by chance。 Clearly； they are acquaintances；
and are working together toward some common end。 I should think it
very l