The uncategorized mystery cases have brought a spiritual detective to the secret of folk legends. She and her squad will discover a feud between two clans that have survived for thousands years of Vietnamese history.

"When a spiritual detective is brought into an unsolved folk mystery, she discovers a feud between two surviving clans of Vietnam..."

some questions pop in head:
1. What do you mean by a spiritual detective?
2. What specifically is this unsolved mystery?
3. What is the secret of the folk legends?
4. What specific visual goal does discovering this feud create for your protagonist?
5. What exactly is the Vietnamese history you are referring to here?

Feel free to reveal your plot (until it messes with the final reveal) and frame it in a logline. Now it would become a long version but from there you can try trimming the unnecessary details.

PS. The "formula tab" on top is really useful.

This is my first tv-series, special thanks to all comments.