Dickens creates a sense of fear in a number ways. Here are three.
1. Imagery that evokes desolation, foreboding, and the supernatural
After the narrator has descended the path and joined the signal-man at his station, he describes the place as a "great dungeon." He comments on the "gloomy" red light and the
"gloomier entrance to a black tunnel, in whose massive architecture there was a barbarous, depressing, and forbidding air. So little sunlight ever found its way to this spot, that it had an earthy, deadly smell; and so much cold wind rushed through it, that it struck chill to me, as if I had left the natural world."
The vivid sensory impressions set the scene. This is the sort of place where the reader can easily imagine seeing a ghost.
The sense of foreboding is furthered by the narrator's first impression of the signal-man himself. For a moment, the narrator says, "a monstrous thought came into my mind…that this was a spirit, not a man."
2. The recounting of uncanny events and deadly episodes
The content of the signal-man's stories is intrinsically disturbing. For instance, when the signal-man reaches out to the dark, mysterious, urgent figure, it suddenly disappears. Then,
"…within ten hours the dead and wounded were brought along through the tunnel over the spot where the figure had stood.”
3. Empathy and fear contagion
Fear is contagious; we tend to become more anxious or frightened when we witness fear in others. More generally, observing distress in others evokes an empathic response. We experience their emotions second-hand. Dickens uses this aspect of human psychology to induce fear in the reader.
For instance, at the beginning of the story, the signal-man reacts to the narrator with great wariness. The narrator is aware of this, noting, "I detected in his eyes some latent fear of me." He wonders if there is an "infection in his mind."
Later, we learn that the signal-man hears the bell ring when no one else can. He believes that it signals the return of the ghost. The reader is left to consider this man's position -- spending long hours, alone in this gloomy place, waiting with anxiety for the bell to ring.
The reader is also influenced by the fearful reactions of the narrator. For example, when he hears the signal-man's story, he mentions the "slow touch of a frozen finger tracing out my spine," and notes that a "disagreeable shudder crept over me."
And when he thinks he sees the ghost he again shares his immediate, involuntary reaction with us:
"I cannot describe the thrill that seized upon me, when, close at the mouth of the tunnel, I saw the appearance of a man, with his left sleeve across his eyes, passionately waving his right arm."
Even the ghost's body language suggests anguish and distress about death:
"It was an action of mourning. I have seen such an attitude in stone figures on tombs."