Please provide a detailed analysis of the story "The Signal-Man" by Charles Dickens, and include themes, an analysis of characters, and important passages.

"The Signal-Man" is a short story by Charles Dickens. It was published in 1866 as part of the Mugby Junction collection. It is a brief but eerie story that follows the narrator's interaction with a railroad signalman.
In this case, we may review characters and important passages together, as many of the story's most important passages reveal important information about the characters.
Characters & Important Passages
There are really only two characters in the story (though other people are mentioned in the narrative). One is the narrator; the other is the signalman.
The story begins with the narrator trying to talk to the signalman near the train tracks. We gather that the narrator is a relatively friendly man and a curious person, too. He calls out to the signalman, asking for permission to approach him. As he does, we catch a view of the signalman from the narrator's perspective:

He was a dark sallow man, with a dark beard and rather heavy eyebrows. His post was in as solitary and dismal a place as ever I saw.

The narrator notices that the signalman seems troubled. When the signalman finally tells him why (he has been experiencing visions of apparitions that are followed by disastrous railway-related accidents, like a train wreck that claimed many lives and the instance of a young woman who died on a train), the narrator is skeptical. He does not believe in ghosts or the supernatural.
As the story goes on, he is increasingly worried for the signalman and feels compelled to help him. He remains practical and analytical even as the signalman seems to be losing it:

He pulled out his handkerchief, and wiped the drops from his heated forehead.
"If I telegraph Danger, on either side of me, or on both, I can give no reason for it," he went on, wiping the palms of his hands. "I should get into trouble, and do no good. They would think I was mad. This is the way it would work:--Message: 'Danger! Take care!' Answer: 'What danger? Where?' Message: 'Don't know. But for God's sake take care!' They would displace me. What else could they do?"
His pain of mind was most pitiable to see. It was the mental torture of a conscientious man, oppressed beyond endurance by an unintelligible responsibility involving life.

Later, when the signalman himself has been killed on the train tracks, the narrator feels that something is wrong before he hears the terrible news:

With an irresistible sense that something was wrong—with a flashing self-reproachful fear that fatal mischief had come of my leaving the man there, and causing no one to be sent to overlook or correct what he did—I descended the notched path with all the speed I could make.

Yet, the narrator remains relatively pragmatic right up through the last lines of the story. Here, he almost sounds like an attorney pointing out the details of a case:







Without prolonging the narrative to dwell on any one of its curious circumstances more than on any other, I may, in closing it, point out the coincidence that the warning of the Engine-Driver included, not only the words which the unfortunate Signalman had repeated to me as haunting him, but also the words which I myself—not he—had attached, and that only in my own mind, to the gesticulation he had imitated.







Other important passages

This excerpt does not specifically relate to character analysis (like the passages above). But it is worth highlighting here because it speaks to the loneliness of the signalman's occupation:

This was a lonesome post to occupy (I said), and it had riveted my attention when I looked down from up yonder. A visitor was a rarity, I should suppose; not an unwelcome rarity, I hoped? In me, he merely saw a man who had been shut up within narrow limits all his life, and who, being at last set free, had a newly-awakened interest in these great works. To such purpose I spoke to him; but I am far from sure of the terms I used, for, besides that I am not happy in opening any conversation, there was something in the man that daunted me.

Themes
One theme revolves around the mysterious causes of disaster. Several of the train-related disasters in the story (the collision and the death of the young woman) were puzzling to the signalman. Though he was having visions and receiving signs that the disasters were tied to the supernatural, the signalman did not at first believe in ghosts or apparitions. The possibility of supernatural occurrences, therefore, is another theme: this story reads like a ghost story or a horror story.
Finally, another important theme is the burden of knowledge. In the story, the signalman keeps receiving warnings of disasters, but he cannot do anything to prevent them—including his own death. What is the point in having information about the future if you cannot do anything to control it? This is a frightening question at the heart of this story.