How do you describe the major theme in a film and explain why it is significant?

Throughout most of the film we see David with Laszlo, as he attempts to unearth the true identity of the man who lies before him covered in burns. He seeks to find out who he is in order to kill him as he believes he is the man who gave away the map for soliders to get through which caused him to lose his thumbs. He wants Laszlo to admit who he is in order to kill him.

We later see Laszlo be mistaken as an enemy by soliders after he walks 3 days in order to get help for Katharine as she lays dying in a cave. He is thought to be an enemy because his name is not English. When he tells this story to David he can't kill him anymore because he knows now who he truly is.