Obviously, Beckett would be the main character. But there could also be a hotel concierge who plays an important role. The concierge could be someone who is either very helpful to Beckett, guiding him around the hotel and the local area, or someone who is a bit of a troublemaker, causing difficulties for Beckett during his stay.
A coworker who has a crush on Beckett might be a main character. They could be the one who stays by Beckett's side the most during his recovery, and this could lead to a romantic sub - plot.
It could be about Beckett having a series of strange encounters at the hotel. Maybe he meets an old acquaintance who brings back memories, good or bad. For example, an old friend who he had a falling - out with and now has to deal with the unresolved issues in this new hotel setting.
The parents of the Beckett baby would surely be main characters. They would be in a state of panic and desperation, driving the story forward with their search for their child.
His doctor could be a main character. The doctor could be portrayed as a very dedicated and empathetic person, constantly providing Beckett with hope and medical advice. For instance, the doctor might have to break some tough news to Beckett about the risks of the transplant, but also encourage him to stay positive.
Beckett is the central figure here as the story revolves around her being hurt in the line of duty. Castle, her partner and love interest, would play a significant role. Additionally, the captain of the precinct might be a main character as he would be involved in the decisions regarding Beckett's situation, such as her leave of absence and the investigation into her injury.
One of the main characters could be the hotel manager. He or she is responsible for running the whole place, dealing with all kinds of problems, from unruly guests to staff issues. Another could be a young bellhop who has big dreams and is always getting into little adventures around the hotel.
In such a fanfic, they could be there for a business meeting. Maybe they meet by chance in the hotel lobby and end up collaborating on a project. Beckett might be a bit reserved at first, but Josh's friendly nature breaks the ice.
The main characters are obviously Beckett and Josh. Beckett seems to be a character who is involved in some sort of relationship that they are about to betray through cheating with Josh.
Obviously, Beckett and his daughter are the main characters. Beckett is likely to be a protective figure, using his skills and knowledge to try and get them out of the trapped situation. His daughter, on the other hand, might be the source of hope or inspiration in the story, perhaps with her own unique ideas to contribute to their escape.
One possibility is that Castle has booked the hotel for a romantic getaway by himself, and seeing Beckett there completely throws him off. Beckett could be there for a much more serious reason, like following a lead on a dangerous criminal. Castle may start to worry about Beckett's safety and decides to stay close to her. As they interact more within the hotel, they might realize how much they've missed each other's company, and this chance meeting could be the start of something new between them, whether it's a new level of friendship or a re - awakening of their romantic feelings.