When the narrator of "The Signalman" first encounters the railroad worker, he is dismayed by the environs of this man: it is, perhaps, the most "solitary and dismal a place" he has ever seen, a subterranean region where a wall of jagged stone drips with moisture, and there is but a "strip of sky" to be seen before the "gloomy entrance of a black tunnel." In short, it seems to the narrator as though he has descended into an unnatural world.
The signalman later reveals to the narrator that he has formerly been a student of mathematics, but was not good; he had also been a student of natural philosophy, but he squandered his opportunities, and it is too late for him to find a career. This sense of futility in the signalman causes him to feel that
He had made his bed, and he lay upon it. [This is an idiom for he has caused his life to be this way] It was far too late to make another.
It is with this same sense of futility that the signalman tells the narrator of a ghost which he has seen twice that calls out, "Look out! Look out!" Each time, a catastrophe has occurred: the train has had a wreck and someone is killed.
The narrator is rather skeptical, thinking that perhaps some mistake has been make, perhaps caused by a malady of "the delicate nerves that work with the eye." He feels that the cry that the signalman hears may be just the wind that makes "a wild harp of the telegraph wires." But, the signalman insists that he has seen and heard accurately.
Then, the man tells the narrator that the ghost returned a week ago. "Ever since, it has been there now and again, by fits and starts," he adds "with increased passion." He tells the narrator that he can get no rest because he is so worried about what will happen since the ghost rang his bell twice the previous night while the narrator has been there.
"Why, see, [says the narrator] how your imagination misleads you. My eyes were on the bell, and my ears were open to the bell, and if I am a living man, it did NOT ring at those times. No, nor any other time except when it was rung in the natural course...by the station communicating with you."
The signalman disagrees, saying that he has never mistaken the bell when the ghost rings it because there is a
"strange vibration in the bell that it derives from nothing else....and I have not asserted that the bell stirs to the eye."
Further, the signalman affirms that he saw the ghost as well. But, when the narrator takes him to the door and has him look out, the man must concur with the narrator that the ghost is missing. So, the narrator departs, although he is worried about his new friend. He promises himself that he will find a physician to help the man.
However, the next night the narrator takes a stroll, and shortly after starting out, he looks down from the brink and sees
the appearance of a man, with his left sleeve across his eyes, passionately waving his right arm.
This is exactly as the signalman has described the ghost. The narrator rushes to the scene and sees some men.
"What is the matter?"
"Signalman killed this morning, sir."
The engineer of the train notes that an accident has occurred. He also tells the narrator that he heard a man say, "Below there! Look out! Look out! For God's sake, clear the way!" So, not only has the signalman been accurate about what has obviously been a premonition, but also the words attached to this ghost, and, perhaps even more eerily, so are the words precisely what the narrator has heard "only in my own mind"; he has not told the signalman about the last movements that the ghost has made. Tragically, now, he believes all that the signalman told him.
While the signalman's narratives have seemed incredible to the narrator (and this reader) because he has been isolated in a dismal and eerie spot which could easily inspire the imagination, ironically, he has been proven accurate.
Thus, because of the signalman's isolation and because the narrator obviously has had some scientific training and is more dispassionate about the occurrences and seems very logical, the tendency has been to afford him more credibility.