Basic plot

• Two lovers, children of rival gang leaders, have a relationship in secret.
  Despite their efforts, their fathers (or one of them) discovers this and orders the assassination of them both.


• The couple are interrupted while together by a ‘hitman’ and are seemingly both killed. Their bodies are thrown into a harbour.


• The girl survives, though injured. Her lover is dead. She is bent on revenge against her father.


• She kills her assassin. She also kills many more people on her journey to her father. She does this seemingly without hesitation.


• Her father discovers that it is his daughter killing his men. Rather than feeling remorse or paternal compassion he steps up his game and orders her immediate death.


• She eventually finds him but leaves him to live, though a broken and helpless man.
  
  The following diagram shows the flow of events as seen in both the feature film and the trailer.

You can see that while most of the pre-climactic events are condensed in the trailer, the 'action' is excluded and so the audience will not feel like anything significant has been given away, since thrillers like this are seen for the characters and action as well as just the storyline.

The final point is not touched on at all in the trailer, obviously, as this would reveal the ending.