With the Nuclear Bomb activated, the city of Gotham is condemned to doom especially with Batman broken by Bane and exiled. The city's entire police force ends up in the sewers locked up, leaving just a handful of Gordon's men on top.
Batman escapes the prison to return to Gotham where he finds an ally in the Catwoman. With his new gizmo 'The Bat' and Cat on the Batcycle, they're up against his re-engineered Batmobiles from the Bane front. With only 12 hours to go to save the city, the city is led to war by freeing the Police force from the sewers against the criminals backed by Bane.
Batman and Bane engage in man-to-man combat with Bane still proving to be more powerful, but Batman, knowing Bane's weakness, takes advantage only to fall into something no-one was expecting - Bane was just the instrument, Miranda/Talia is the source!
(Miranda the philanthropic rich lady is in fact Ras Al Ghul's daughter, and the one who was born in the prison and the only one previously who escaped. She was helped by Bane, who was badly beaten for aiding her escape. The mercenary, Ras Al Ghul, returns and takes pity on Bane, recruiting him to the League of Shadows ... before soon banishing him for being too extremist)
Talia's plan to detonate the city is foiled by Gordon with Batman's help, but the city still is in danger as the nuclear core has to reach the reactor to stabilize. The CatWoman, in some thrilling chase of the nuclear bomb, helps Batman stop Talia but to no avail. Talia floods the nuclear base leaving Batman with no option but to take the bomb far into the sea, away from city's harm!
In what would be a more commercial end to things, the film shows an end to the Batman saga, only to see how John Blake a.k.a Robin discovers Batman's secret hideouts, Gotham rebuilds itself from the ashes and lastly, how Alfred's dream comes true...
(As it ends, we're in Florence where Alfred is taking his annual vacation. He sits at his usual table and orders a drink. As he looks around he sees a familiar - Bruce Wayne, sitting at a table with Selena Kyle, who raises his glass to his old friend. Alfred, in relief, gets up and leaves in peace.)