Unless you start a book with a birth day, your characters are already fully fledged people with personalities and attributes. Plunging into their lives with little knowledge of their backgrounds, their pasts and influences, means there is a mystery about them.
I’m not writing a biography, but somehow there needs to be a background development for each key character. I need to unpeel the layers of an onion to expose attributes, behaviours and salient moments in their lives. I prefer to work this unpeeling around the plot or dialogue. Sometimes it needs to be done early in the book and for others, it can be left. Since I’m writing a series I can unravel my characters over time and crack into them gradually. Perhaps, for one cast member, not expose his past until quite late into the story. Others need their backgrounds brought into the foreground as part of the narrative.
Jason is a character I keep as an enigma. Gemma’s past is very relevant to the story. What happened to her? How did she come to be wandering into a new job and detached from her friends and family. Why does she have nightmares and struggle to free her tears?
The book is not about exploring her past trauma in detail and neither is it a whodunnit with regard to her abuser. It is what happens next which is key to her struggle to heal her damaged emotions.
I have added a short story showing where things started to go wrong for Gemma. It is as far as I will go now. The rest unfolds in the books.