I'm not sure specifically as I haven't read this exact story. But generally, it might be about a man's journey on a train, perhaps his encounters with other passengers, his thoughts during the ride, or something extraordinary that happens during the train trip.
I'm not sure which specific 'A Man on a Train with a Dog' short story you are referring to. There could be many stories with such a premise. It could be about a man traveling on a train with his dog, and maybe they have an adventure during the journey, like meeting interesting people or getting into a small mishap. But without more details, it's hard to tell the exact story.
Not having read 'the man on the train short story', it's difficult to determine the main characters precisely. The man on the train is surely a central figure. There could be a mysterious stranger sitting next to him, who is also a main character and whose actions or words drive the plot forward. Additionally, there might be a family on the train that the man interacts with, and they play an important role in the story as well.
A train journey can turn into a horror story if there's some sort of supernatural element involved. For example, seeing apparitions in the train corridors or feeling an unexplainable coldness. It could also be due to a dangerous criminal on the loose inside the train. Passengers would be in a state of constant fear not knowing when or where the criminal might strike. And if the train gets lost, like going on a wrong track that leads to an abandoned and creepy place, that would surely make it a horror story.
Common themes in train horror stories include the idea of being trapped. Once you're on a moving train, it's not easy to just get off. So if there's a threat on the train, you're kind of stuck there. Also, there's the theme of time. Trains usually run on a schedule, but in horror stories, that schedule can go haywire. For example, the train might keep going and going without stopping at the right stations. And finally, there's the theme of the other passengers. There could be a person on the train who seems normal at first but then reveals themselves to be a monster or a threat in some way.
He might be a traveler. You know, someone who loves exploring new places and is using the train as a means of transportation to reach his next destination. He could be from a different country, with a whole different culture and background, which might play a role in the story as he interacts with other passengers on the train.
I'm not entirely sure which specific 'Train Man' the novel refers to without more context. It could be the name of a character. There might be a story in the novel centered around this 'Train Man' character, perhaps his experiences on a train or his journey in life that is being told.