More formal:
* Within the narrative
* In the text
* In the fictional account
* Throughout the plot
More informal:
* In the tale
* In the book/article/film
* In the plot
* Throughout the story
More specific:
* In the first chapter
* In the climax
* In the character's backstory
* In the setting of the story
Other options:
* As depicted
* As described
* According to the story
* As the story unfolds
The best alternative will depend on the specific context and tone of your writing.