A occult detective finds herself in a world of supernatural beings in dystopian America.

Hello IvyEight6,
How about:

Investigating America's post-apocalyptic occult cases, a female detective discovers an inexplicable world of supernatural entities.

I hope this helps.

1) I meant a detective who investigates occult cases.
2) The world is post apocalyptic.
3) She encounters them.

Hi IvyEight6,
I personally like where you are going with this logline. That's why I need to know the answer to the following questions in order to help/review.
Do you mean an undercover detective by an occult detective? or do you mean a detective who investigates occult cases?
What other word/s can you use instead of "dystopian"?
How does the detective find herself in the world of supernatural beings?