is the physical similarity between Stapleton and Hugo Baskerville
that, at the end of the novel, provides the detective with the missing element he needs to arrive at the truth.
A second type of clue, one of the best-known, is the print, or the trace left directly by the body of the criminal. A particularly
common trace is the footprint, human or animal. Both of these types of prints can be found in The Hound of the Baskervilles (left by the hound and by Sir Charles Baskerville) and in fact play a determining role in the case; it is by deciphering
these prints that Holmes is able to analyze Sir Charles’s death.
A third type of clue is the indirect trace left by the criminal. One of them is tobacco, on which the detective, the author
of a monograph on the subject, is an expert. His interpretation of the cigar ash allows him to feel certain that Sir Charles,
just before his death, stood for some while in front of the wicket-gate giving onto the moor. In a more anecdotal way, a cigarette
stub allows Holmes, when he comes back to his moorland hiding place, to guess that his visitor is Watson. *
A fourth kind of clue is the written document. This type comes in at two essential points in the investigation. In the beginning
of the book, the examination of the anonymous letter urging Henry Baskerville not to go to the moor allows Holmes to affirm
that it was written in a hotel using a Times editorial. At the end of the book, the study of the fragment of a letter written by Laura Lyons leads the investigators to
guess that this letter was intended to lure Sir Charles Baskerville into a trap.
A fifth type of clue concerns objects. For Holmes, objects have their own life and thus are capable of giving valuable information
about their owner; they have the same value as written documents. This “reading” of objects is present in The Hound of the Baskervilles , even though it is used only for anecdotal purposes. The study of the cane left by Dr. Mortimer in Holmes’s flat at the beginning
of the story helps the detective and his friend form a precise picture of its owner and of the circumstances in which the
object was presented to him. What’s more, the examination of Watson’s clothes, in the same opening scene, allows Holmes to
guess that he spent the day at his club.
But observation of clues is not restricted to the study of material elements. It also concerns psychological behavior , which according to Holmes can be reconstructed with as much precision as actions that produced material clues. Just as matter
itself is legible, the way individuals behave also constitutes a source of instruction, whether or not the detective was actually
there to observe that behavior.
This study of behavior is alluded to in the scientific monograph, written by Holmes, that forms the occasion for his conversation
with Watson in A Study in Scarlet : “The writer claimed by a momentary expression, a twitch of a muscle or a glance of an eye, to fathom a man’s inmost thoughts.” 21
Psychology here should be taken in its broader sense; it is not just mental operations that are in question, but the totality
of ways in which living beings react and express themselves without realizing it. Thus in the scene in which Holmes meets
Watson, it is Watson’s general demeanor that allows Holmes, at one glance, to guess that he is by profession an army doctor.
This second series of clues is just as important as the first in the solution that Holmes proposes at the end of The Hound of the Baskervilles . At the outset of his investigation, he pays attention to the behavior of the murdered Sir Charles Baskerville, and especially
to the fact that he decided to wait in front of the gate giving onto the moor, then began walking on tiptoe as he moved away
from his house. In this instance, the material clue is reinforced by a psychological clue.
Attention to human behavior also drives the accusations Holmes will make