Set in the 1950s amidst the hustle and bustle of New York City, Lionel Essrog (Edward Norton) runs a detective agency with his companions Gilbert Coney (Ethan Suplee), Danny Fantl (Dallas Roberts), and Tony Vermonte (Bobby Cannavale). Their lives changed thanks to their mentor, Frank Minna (Bruce Willis), who rescued them from orphanages, offering them a sense of family and purpose. Although Lionel possesses a sharp mind, his struggle with Tourette's syndrome gives him an air of eccentricity, leading to a rather reclusive lifestyle. However, his condition also affords him an extraordinary memory that proves invaluable in his detective work.
One day, Frank is embroiled in a secretive job and enlists Lionel and Gilbert to keep an eye on him during an important meeting. As they eavesdrop over the phone, they learn that Frank is negotiating critical information linked to a powerful group consisting of William Lieberman (Josh Pais), Lou (Fisher Stevens), and a menacing henchman. When things turn chaotic, Frank is ambushed, leaving Lionel and Gilbert powerless to prevent his tragic fate.
In the aftermath, Frank's widow, Julia (Leslie Mann), appoints Tony to oversee the agency. Fueled by a quest for justice, Lionel dons Frank's hat and coat to channel his mentor’s spirit and delve deeper into the mystery surrounding his death. His investigation leads him to a matchbox and an African-American bar, prompting him to piece together fragments from Frank's last conversation. He discovers Laura Rose (Gugu Mbatha-Raw), involved in a fight against gentrification, is key to Frank's pursuits. Critically involved in this battle against displacement is Gabby Horwitz (Cherry Jones), causing Lionel to attend a public meeting where he encounters Moses Randolph (Alec Baldwin), the architect of the city's gentrification.
Through clever disguise and determination, Lionel befriends Laura while exploring the complexities of the gentrification issue. However, a misunderstanding leads to a confrontation with her father, who mistakes Lionel for an adversary. After his rescuer, a club trumpet player (Michael K. Williams), provides refuge, Lionel uncovers evidence of corruption surrounding property dealings led by Moses and leverages this knowledge to protect Laura.
The stakes rise as Lionel receives a warning from Laura’s father, only to find him murdered upon arrival. Distressed, Laura confides in Lionel about her lineage, leading to shocking revelations about her true parentage. In a race against time, Lionel confronts Paul Randolph (Willem Dafoe), discovering his connection to Moses and the underlying schemes that threaten Laura’s life.
In a gripping confrontation, Lionel dodges danger and exposes Moses's sinister history while demanding Laura's safety and revealing the truth to the world. > "Motherless Brooklyn," Lionel subtly deploys the clues and confronts various adversaries in a climatic journey filled with twists that redefine loyalty, justice, and the power of truth. Ultimately, he seeks not only answers but also a future for Laura, emphasizing that some battles are worth fighting, especially for those we hold dear. As events unfold, Lionel’s pursuit culminates in a confrontation that promises both resolutions for the past and hope for a new beginning as he drives to the property tied to Frank's legacy, where Laura awaits.
