The year was 1920 and Gotham was undergoing an extensive renovation thanks to the vision of Jack Wayne. Jack tries to grease the palms of Gotham's finest to clean up the slums of the criminal element in order to make his future establishments appealing to outside businesses. Unfortunately, police brutality soon followed and those less fortunate suffered for the abuse of authority. This series of unjust arrests gained the attention of a young brute named Brass. Brass got his moniker because he was a natural born leader who organized his own army of juvenile thugs. Brass would instigate bouts between Jack's construction workers and lead Gotham PD into bottlenecks where they would come under attack by bricks that were thrown from the rooftops.
Eventually, the law caught up with Brass when Detective Loeb set a trap for Brass. Loeb presented Brass to Jack Wayne because Jack wanted to know who was responsible for the constant delays in his projects. When Jack learned that a child was the ringleader of these disturbances, he was actually impressed rather than upset. Jack told Loeb that he didn't want to press charges against Brass and offers Brass a position in his operations. Brass helped Jack expand in the slum development business because there would be a demand for low cost housing during the impending Great Depression. Brass also demonstrated his loyalty to Jack by exposing Jack's right hand man Smitty has a thief who was skimming off the top with material thefts and cost padding.
As Brass got older, his methods of persuasion became more violent especially toward a Jack's former Union organizer Huston. Jack didn't approve Brass' brute force toward Huston even though he was corrupt. Brass managed to calm Jack's disappointment by informing of a new enterprise that could make Jack even more money. Brass starts associating with a rum runner named Scabetta. Brass helps Scabetta store his hooch in the Straight Pope, a series of the coastline caverns underneath the eventual Wayne Manor. Brass tells Scabetta that he could help launder his dirty money by establishing an amusement strip that could rival Atlantic City. Scabetta likes the idea but thinks Jack Wayne could pose a problem. Brass convinces Scabetta that he keeps Jack Wayne wrapped around his little finger just as long as he is making Jack money.
Brass fills Jack in on the latest developments and the recent flow of capital. Jack was pleased with Brass' results and just as Brass was about to pitch the idea he suggested to Scabetta, Jack is struck by a car that entered the sidewalk. Brass recognizes the driver as Smitty, the embezzler who stole from Jack. Brass tries to catch up with the getaway car while Thomas Wayne uses his shirt as a tourniquet to stop his father from bleeding out. At the hospital, Jack apologizes to Thomas for all of his the criticisms towards Thomas' fascination with medicine. Brass is injured a little bit by Jack's newfound fondness for Thomas but he brushes it off when Jack puts him in charge of keeping the wheels turning and making money for the Waynes.
Brass uses his thugs to put an end to the labor strikes and starts putting a hold on the construction of Wayne Manor. Jack arrives at the construction site of his new home to confront Brass about his latest act of aggression. Brass tries to convince Jack in halting the construction of Wayne Manor because it will interfere with the land development deal he made with Scabetta. Brass reveals Scabetta as his financial backer but Jack tells Brass that he refuses to get in bed with a gangster. To Jack, rum running was one thing but laundering money for the mob was quite another.
As a last desperate attempt, Brass tries to bribe Jack with a briefcase full of gold bricks from Scabetta in order to change his mind in finishing Wayne Manor. Jack tells Brass that the answer is no and in a fit of rage, Brass tosses the case full of gold bricks down the secret elevator that Jack's grandfather used to help runaway slaves from the Underground Railroad. With Jack's stern refusal, Brass had no other choice but to run because Scabetta would come after him for failing to convince Wayne into giving up Wayne Manor. Brass went onto participate in World War II, the Korean War and finally Vietnam.
Brass eventually returns to Wayne Manor during the engagement party between Thomas and Martha Wayne. Brass makes a scene about his return to Gotham in front of Jack's guests. Jack pulls Brass aside and shows him to his office. Jack tells Brass that he has no business in his home especially after the negative stigma that Brass created during his employment with Jack. Thomas interrupts their conversation and reaffirms his father's request that Brass should leave. Brass tries to convince the Waynes that the wars have made him a changed man but Thomas knows otherwise. Thomas has been following Brass' exploits as a master strategist but he's also knows that Brass is a soldier fortune. Brass has been brought before his superiors more than once for unsubstantiated charges or war profiteering and black marketing.
The final straw for Brass was when Thomas mentioned how he was almost dishonorably discharged during his occupation in Japan. Brass reacts by insulting Thomas for his accusations and tells Jack that he would have never achieved his architectural vision of Gotham's future if it had not been for him. Jack tells Brass that it was his so called ingenuity that cost him a fortune in the long run. The union workers who went on strike and were brutalized by Brass, got lawyers in order to force Jack into making amends. Jack settled by ensuring a well paid education for each of the worker's children and guaranteeing their demands for pensions. Jack knew that these restitutions would cost him so he used Brass' ill gotten gold to compensate the terms set by the workers' lawyers. The argument between Brass and Jack got so heated that Jack's heart finally gave out and he died on the office floor.
Brass abruptly leaves in order to avoid any complications with the police but he wasn't going to take this lying down. A few years had passed and Bruce was already a kid. Thomas and Martha throw a Halloween charity gala for the Wayne Foundation but unbeknownst to any of them, Brass decides to crash the party. Brass enlisted a few men from the Maroni mob to help in distracting guests at the gala so he could have a clean shot at Thomas Wayne. Maroni's men were getting impatient and decided to react rather than take Brass' orders anymore. Maroni's men started demanding everything from gala's guests and the guests erupt into a panic.
Men like Thomas Wayne fought off Maroni's men while the women and children made their way out of the ballroom. As for Brass, his clean kill shot was ruined when Thomas sucker punched one of Maroni's men and the hitman's gun went off. The bullet ricocheted and it hit Brass in his right shoulder. Despite his injury, Brass managed to escape without being seen by fleeing with the rest of the panicked guests. It remains unknown as to why Brass wears a protective head plate to cover the right side of his skull even to this day. Brass left Gotham to become a gun for hire but he did vow to one day return to Gotham and take his revenge on the Wayne Family.
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 was 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 begins to tremble. Bruce and Priest are knocked off a cliff side 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.