It's likely not a true story. Usually, such works are based on imagination or inspired by various ideas rather than real events. The plot and characters might be crafted to engage the audience rather than being based on facts.
The 'infidel true story' could be about many things. It might be a story of someone who is considered an infidel in a particular religious or cultural context and their journey. It could involve their struggles, beliefs, and how they are perceived by others in that society.