Destroyer follows an LAPD cop who, as a young officer was placed undercover with a gang.
The experience has had long-lasting consequences on the officer which come to the forefront when the leader of the gang emerges many years later.
And we see the woman she has become now as a result.
In the trailer, we see the story shift back and forth between the two time periods and we get glimpses of what the character was forced to do, and what she may have done by choice, in order to integrate herself into the gang.