In 1950s New York City, Lionel Essrog works at a detective agency alongside Gilbert Coney, Danny Fantl, and Tony Vermonte. Their boss, Frank Minna, rescued them as children from an abusive orphanage. Nicknamed "Motherless Brooklyn" by Frank, Lionel has
Tourette syndrome and
OCD, often alienating him from people, but his strong
verbal and
photographic memory make him a good detective. Working a secret case, Frank asks Lionel and Gilbert to shadow him to a meeting. Lionel listens over the phone as Frank presents documents that threaten a business deal for a man named William Lieberman, who's there with his assistant Lou and an extremely large henchman. When Frank tries to negotiate a high price, the men force him to take them to the originals. Lionel and Gilbert follow in their car, arriving just as Frank is shot. They take him to the hospital, but Frank dies. Frank's widow Julia leaves Tony in charge of the office. Lionel begins wearing Frank's hat and coat, and a matchbook in Frank's pocket leads Lionel to an African-American owned jazz bar in
Harlem. He realizes that Frank's findings involve Laura Rose, who works for Gabby Horowitz fighting
urban renewal; poor and minority neighborhoods are being bought out and demolished, forcing out their residents. Lionel goes to a public meeting where Moses Randolph, a commissioner of several development authorities, is loudly contested by Horowitz and the audience. Stealing a reporter's credentials, Lionel talks to a man named Paul who raged against Moses at the meeting and tells him Moses is the real power in the city government, even beyond the mayor. Under the guise of reporting on the urban renewal story, Lionel gets to know Laura. She takes him to a club Frank was investigating, where her father Billy assuming Lionel is one of Moses' men has him beaten unconscious. Lionel is rescued by a trumpet player, and discovers that Paul is Moses' brother and an engineer. He realizes Lieberman is receiving
kickbacks on many of the housing deals, and that the housing relocation programs are scams. Paul presents Moses with a huge renovation plan to improve the city. Billy calls Lionel, apologizing for the attack and offering to meet with information. However, Lionel arrives to find Billy murdered with his death staged as a suicide. Staying the night with a distraught Laura at her house, Lionel admits his true identity and that he believes she is in danger. Finding photos of Paul meeting with Billy on his own, Lionel confronts Laura, who explains that her "Uncle" Paul is her real father. Paul denies this to Lionel, and explains that Frank and Billy planned to get more money out of Randolph's goons, against Paul's protests. He begs Lionel to find the evidence. Lionel is brought to Moses, who invites him to join his team and stop snooping, with 24 hours to decide. Inside Frank's hat, Lionel finds the key to a
Pennsylvania Station storage locker, containing a property deed and Laura's
birth certificate, which reveals Moses is her father. Lionel gives the key to Paul and runs into Tony, who has been working surveillance for Randolph. Tony admits he has been sleeping with Julia, and tells Lionel to take Moses’ deal since Laura will soon be killed. Lionel races to save Laura, stopping her before she enters her apartment, and they flee. Laura knocks the large henchman off the fire escape, and Lou corners them with a gun but is hit in the head with a trumpet by the trumpet player, who drives Laura out of town. Lionel meets Moses, who reveals that he raped Laura's mother, a hotel employee. Paul forged Moses' signature on the birth certificate and exposure of this secret threatened Moses. Lionel warns Moses to leave Laura alone or he will release the information. He informs Moses that Lieberman is on the take and asks that when Moses has Lieberman killed, to tell him it is for Frank. Moses tells Lionel to tell Paul that his plans for the city will proceed. The next day Paul learns that Moses denied his plans out of spite while Lionel mails the information about Lieberman to the reporter whose credentials he stole. Lionel drives to the seaside property Frank left to him where Laura is waiting for him.
Differences between movie and book Norton took significant creative license with Lethem's book, keeping only the character of Lionel Essrog, his mentor Frank Minna, and the idea of him investigating his surrogate father's murder; deviations
The Atlantic's David Sims considers "both radical and baffling". , controversial urbanist that inspired the character of Moses Randolph Although the novel takes place in a modern 1999 setting, Norton rewrote the story for the 1950s, because the "characters are written in a very 1950s hardboiled detective style ... and if we try to make a film about the '90s in Brooklyn with guys acting like '50s gumshoes, it will feel ironic." Norton added characters such as Moses Randolph to the story, who is based on the New York City urban planner,
Robert Moses while dropping others, such as Frank Minna's brother Gerard. and he replaced the book's love interest Kimmerly with Laura, the unknowing daughter of Moses Randolph. Lethem spends considerable time in the book depicting Lionel's childhood at the St. Vincent's Home for Boys orphanage, something the movie only briefly references. While the book ends with Lionel going back to the detective agency turned car service, with his love interest leaving him, and most of his friends dead or missing, the movie ends with Lionel together with Laura considering a life outside Brooklyn. ==Personal engagement==