The Dark Knight Rises is the end cap to Christopher Nolan's Batman trilogy. The film begins with Batman not having been seen in the eight years since Harvey Dent was killed and there is peace in Gotham as criminals are being held under The Dent Act. The film is about paying the ultimate price in order to complete becoming a symbol of hope for the people of Gotham. Batman has always been whatever the people off Gotham have needed him to be whether that's scapegoat, hero or murderer. Whatever he represents he represents it for the betterment of the people of the city. And with peace on the rise Batman is seemingly no longer needed.
But, just as peace has risen there comes a changing tide as Bane and his mercenaries move into a Gotham unoccupied by Batman in order to create chaos and level the city with a nuclear bomb. Batman must make the decision to come out of hiding in order to save the city at the risk of being gunned down by the police force himself for Dent's murder. And when Batman returns the police are more concentrated on taking him down than going after the real threat, as they desire to become heroes for taking down the Batman. But with their eyes focused on the Dark Knight, Bane is able to continue to build his army underground and right under the noses of the police and the people of Gotham, and before they know it the city is no longer theirs. It belongs to Bane as he has used the fear of the bomb going off to stifle any rescue attempts by the military or any escapes by the people in the city.
Thus, Bane uses the truth of Harvey Dent's death to turn the people of Gotham against the police and towards anarchy. He turns the poor against the rich and tears down the walls of any remaining class structure. By doing so he does not need to control anyone. He simply gives permission to people to act in accordance with how they feel. The only difference is that there are no consequences for hurting anyone.
Batman thus returns to restore the balance of order and justice by standing for what is right even when everyone else is standing against him. Even to the very end Batman believes every person of Gotham deserves to live. He believes it so deeply that he is willing to sacrifice his life for them because he believes in the power of a symbol, and giving ones life for others is the greatest sacrifice anyone could make for another. Thus Batman becomes a symbol of taking care of one another and defending the poor and innocent from the criminals and those that seek to take advantage of people. He becomes a symbol that anyone can be a hero at any moment so long as they have the courage to do so.
