Witness

The Trailer : 

Witness is a thriller released in 1985. 

This movie talks about a young boy who is the witness of a crime. At first, the culprits didn't really know if the kid had seen the crime but when they understand that it's the case, he became a danger for them and they want to kill him.

 So, a detective (Harrison Ford) tries to protect him and his mother bringing them in Philadelphia but as the killers are still prosecuting them, then he decides to hide them in the countryside. The policeman and the mother fall in love with each other and begin a relationship but the bad guys are still looking for them and seem determinated to catch up them...

With the end of the trailer (when the guy say "I know where you are" and then we see three men, two of whom have guns, walking toward a farm in the countryside), I expect to view a final crime with the sacrifice of the man who is played by Harrison Ford so as to safe their life and the woman could killed the bad men to protect her son. I expect a dramatic end with the detective's death but not entirely dark with refound freedom of the mother and the child.