Even if it's a completed story and there's no script for it yet, you can still write a logline using the format that B8C outlined for you.
Perhaps something like:
Major Event: His wife dies and children go missing
Hero: A grieving Mexican luchador
Main action: Find his children and break up the biggest human trafficking ring in Mexico.
Example logline:
After his wife dies and his children go missing, a grieving Mexican luchador must find his children and break up the biggest human trafficking ring in Mexico.
I know there are some points missing, but just to give you an idea of how you can boil it down to its core elements.