Years had passed and Col. Brass had taken on his last assignment. In the Middle East, Brass was under the employ of a vicious dictator but at the same time Brass aided the rebel cause. Brass' only goal was to be paid for his services. It didn't matter whose cause would win or who would lose their life just as long as he got his cut of the profits. Just as he was about to leave the dictator to his fate, Brass comes under surprise by a squad of me who were still loyal to the dictator. However, with the mere snap of Brass' fingers, a chopper rises from the chaos outside and opens fire. The calculated shower of bullets cuts down everyone in the dictator's office except for Brass who stands tranquil with a smirk on his face. Brass turns to the chopper to praise his men for a job well done but the dictator had survived the ordeal and tried to make a pass at Brass with his gun. Unfortunately, Brass saw the dictator at the corner of his eye. With the flick of his wrist, a trick blade springs out and Brass takes a swing at the dictator's gut. The dictator's intestines spill out over the floor as Brass cleans his blade.
When Brass returns to his base of operations, he comes to realize that he has come to crossroads of his life and now he must decide what to do with his final days as a cold blooded warrior. His first item of business is to return to Gotham and interact with Bruce Wayne's old flame Silver St. Cloud while his foot soldiers terrorize the streets of Gotham by instigating an all out gang war. Brass wants St. Cloud's real estate connections in order to establish a convention in Gotham. The convention will serve as Brass' new base of operations and as a recruiting center for any mercenaries who want to join Brass' siege on Gotham. Brass presents the mercenaries with an enterprising agenda to steal from Gotham as they instigate a citywide gang war which will keep Gotham PD and the Batman distracted.
Brass gives Priest, his second in command, a special task to starting the gang war. Priest must procure all ledgers and books that dictate the mob's illegitimate gains. One book keeper in particular begged for his life but Priest viewed the book keeper with disgust because he finds that a man defines himself when he dies. Priest offers "a brave death" to all of his enemies and asks the book keeper to maintain some form of dignity as he placed a grenade in the book keeper's mouth. As the book keeper prepared for the end, he noticed Priest's buck knife was in reach. Priest noticed what the book keeper was looking at and taunted him by goading him to take the knife. The book keeper began to sweat with tension but in the end, he cowered on the floor and Priest pulled the pin. The book keeper's office was engulfed by a fiery explosion.
Brass uses his knowledge of Old Gotham to devise a shipping route to the convention center thereby enabling his hired guns to secretly gain access to the latest advancements of artillery and explosives. The Spur Line became a forgotten railway according to the city's plans but Brass' memories of Old Gotham are as fresh as they were over 60 years ago. Brass reaches the convention center to make sure his operation is kept a secret from Silver St. Cloud who thinks she is organizing a security advancements expo.
Brass arrives to meet with Silver and asks her to take the rest of the day off for all her hard work as an arms convention publicist. Silver agrees but just as she was making her way to the lobby, she overhears one of Brass' thugs talking about the how Spur Line is a good cover. Silver continues to listen to the conversation until she is discovered by other members of Brass' squad. They chase Silver to the lobby where she tries to call the night watchman for help but it turns out to be Brass. Silver reacts quickly by activating the silent alarm but ends getting stabbed by Brass with an ice pick he stole from a local thug that his men killed earlier.
Fortunately, Brass didn't puncture any crucial arteries and Silver was in a stable condition when she went Gotham Mercy Hospital. Bruce arrives on the scene after Silver's ambulance drives off. As Batman, Bruce investigates the inner workings of this supposed convention. He disarms to guards who were working for Brass and discovers that the basement of the convention has a secret passage that leads to the Spur Line. Batman deduces that the Spur Line must be the method that the gun runners are using to get around Gotham without being detected. Bruce also figures that the gun runners are the orchestrators behind the gang war but he doesn't know what the end game is if the gang war is a diversion.
Meanwhile, Brass gives the order to lay siege to Gotham by destroying the financial district of Gotham such as Diamond Exchange and Gotham's First National Bank. Batman goes to intercede and stem the blood shed. Batman makes quick work of Brass' mercenaries and learns a few things by interrogating one of the mercenaries. It turns out Brass supplied the rival gangs with new artillery after instigating the gang war as a distraction for the police and the Batman. However, Batman finds this latest attack to be sloppy on Brass' part because Brass would have presumed that one of his mercenaries might be caught during the siege and could divulge his involvement with the gang war or gun running. Unfortunately, things start to make sense for Bruce when he receives a distress call from Alfred.
Batman arrives to immobilize one member of Brass' squad who securing the grounds while Alfred takes on another squad member in the basement. Brass and another member of his squad make their way to the lower foundations of Wayne Manor by using explosives. Batman enters Wayne Manor through the library but he comes under attack by Priest. Priest proves to be a formidable combatant for Batman but Bruce's usage of theatricality trips up Priest. Batman finally puts an end to Priest by throwing him out a window. Batman then makes his way to the cave to put an end to Brass. Brass decides to shoot his squad member because she refused to be involved in his revenge plot against the Waynes. Brass is then taken by surprise when Batman throws a batarang which knocks the gun out of Brass' hand.
Batman demands to know why Brass has a vendetta against the Waynes. Brass explains his past relation with Bruce's grandfather and how he figured out Batman's secret identity. Brass remembers Thomas' bat costume during the Halloween gala that he tried to crash. Brass immediately put two and two together when the Batman was first sighted. Brass confesses that he decided to take his revenge on the Wayne family now because his time on this Earth has reached its pinnacle. The cancer in Brass' body has begun to spread and he refuses to go down without taking the Wayne legacy with him. Brass and Batman combat each other but Bruce's vigor overpowers Brass.
Unfortunately, Priest intervenes and tries to defeat Bruce. Bruce gives Priest a second serving of pain but fails to stop Brass from committing suicide. Brass reveals that he has explosions strapped to him and activates the detonator in the hopes of taking Wayne Manor down with him. The magnitude of the explosion incinerates Brass and the entire foundation to tremble. Bruce and Priest are knocked off a cliffside in the caverns. Bruce manages to grapple to safety but Priest falls to his death when his body hit the rocky river bank beneath the caverns. In the end, the strong foundation within the Batcave kept Wayne Manor standing but Bruce was still unable to reconcile his rocky relationship with Silver St, Cloud.