What is the significance of the supernatural to the plot development in Dickens' "The Signal-man?"

In Charles Dickens' short story, "The Signal-Man," what
makes the story so scary and wonderful is Dickens' use of the supernatural. This was not
unheard of for Victorian writers; in A Christmas Carol, Dickens
uses the supernatural extensively. The experiences Scrooge has with "ghosts" move the
plot along and are responsible for his change of
heart.

Dickens provides information regarding the
supernatural early on in this story, creating the mood. The first
paragraph alludes to supernatural forces at work. When the visitor hollers down, the
signal-man can't tell where the voice is coming from—it's like a "disembodied" person
speaking. Instead of looking up to where the speaker is standing above him, the man
first looks down the railroad line, an unusual
reaction since the voice had not come from that direction. It is here that we
might first suspect that the signal-man has a problem. The signal-man is first described
as "foreshortened and shadowed," almost like a creature from another
world.

When the signal-man looks at the speaker, he
carefully studies him—there is something unusual in that the signal-man seems as if he
doesn't trust his visitor. When the narrator approaches, the
signal-man is watches him carefully, almost as if the visitor is an
apparition!

The railroad tracks create an unusual feeling
for the narrator. The shadows and color add to their eeriness, and the speaker
experiences a strong uneasiness.

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So little sunlight ever found its way to this
spot...and so much cold wind rushed through it, that it struck chill to me, as if I had
left the natural
world.

Early
indications show the signal-man to be unusual—is he sane?Alone too much on the job? The
signal-man explains that the visitor looks familiar, which is why he studies him. The
signal-man is described as "remarkably exact and vigilant"—so he is a reliable
person. Finally the signal-maker declares that he wants to share his worries with his
visitor, if he will returns a second night. The visitor agrees—and
in this moment, the signal-man introduces his fear for the first time. When he asks why
the narrator called to him with the exact words he chose to use,
and the signal-man asks:

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You had no feeling that they were conveyed to you
in any supernatural way?

The
speaker says no, and agrees to come the next night. When he arrives, immediately the
signal-man relates his past experiences. The visitor looks like an apparition that has
twice appeared on the tracks, waving a warning. When the man first followed the
"vision," he disappeared. The visitor tries to explain that the image was in the
worker's mind, but then the man describes a similar instance with
the same ghost that later heralded a woman's death on the train. The specter has now
returned a third time, and the signal-man is worried: what is the warning? How can he
warn or help anyone?

The following (third) evening, the
visitor arrives and, looking down the track, sees a man waving as the signal-man had
described: he is actually showing other men what he saw—the narrator asks and learns the
signal-man was killed earlier by a train. The words the engineer used were exactly what
he had heard earlier. The warning was for the
signal-man.

The entire story moves along with
the introduction of supernatural events: apparitions that disappear, and words and
gestures of warning. It is the supernatural that creates the mood and drives the plot,
for what the signal-man heard and saw foreshadowed his own
death.