“Motherless Brooklyn” often frustrated me but engaged me enough at least. Although I sometimes struggled to gather what is exactly going on around its inherently flawed detective hero throughout most of its running time, I enjoyed a number of offbeat qualities mixed into its laid-back narrative, and I observed its increasingly complicated mystery plot with some care and attention even while recognizing its weak aspects.

Edward Norton, who also directs and co-produces the film in addition to adapting Jonathan Lethem’s novel of the same name, plays Lionel Essrog, a private investigator operating in New York City in the 1950s. Although he has frequently struggled with Tourette syndrome since his childhood, Lionel is pretty good at remembering things he sees and hears, and that is the main reason why his mentor/boss Frank Minna (Bruce Willis) took young Lionel under his wings many years ago. Because Frank saved him from his miserable time in an orphanage after his single mother’s early death, Lionel has been always loyal and grateful to Frank, and Frank has always trusted Lionel more than three other guys in his detective agency, who were also orphans just like Lionel.

At the beginning of the story, Lionel and one of his colleagues are assisting Frank for some important meeting between Frank and his latest client, but things soon go horribly wrong during the meeting. Lionel and the aforementioned colleague, who have been monitoring the meeting from the distance, try as much as possible for saving Frank, but, unfortunately, Frank is murdered in the end, and Lionel and others in the detective agency are certainly devastated by that.

Haunted more and more by how he could not save Frank at the last minute, Lionel becomes quite determined to find why Frank was killed, but, of course, the task turns out to be more demanding and challenging than expected. While a number of seemingly important clues including Frank’s last words are in front of him, Lionel does not have any idea on how they can be fit together to give him the answer, and he also suffers more from Tourette syndrome as his mind often becomes more agitated than usual. Whenever he becomes too nervous and excited, he involuntarily utters meaningless words, and that certainly causes awkwardness between him and others around him.

And then, of course, things become a little clearer to Lionel as the plot thickens. It is subsequently revealed that Frank tried to blackmail his latest client via something he recently discovered through his investigation, and that seems to be involved with a young African American woman named Laura Rose (Gugu Mbatha-Raw), who also happens to be associated with a man running a certain jazz bar in Brooklyn which seemed to draw Frank’s attention for some unknown reason.

In addition, Laura has worked as an activist fighting against the upcoming urban renewal plan of the city administration. This plan looks beneficial for those poor residents of Brooklyn on the surface, but many of them, who are incidentally colored people, are not so pleased at all as they are forced to leave their impoverished neighborhoods without any benefit, and those high-ranking officials including Moses Randolph (Alec Baldwin) do not give much damn about the angry protest from these people, while quite determined to push the plan forward by any means necessary.

After meeting and then talking with a mysterious guy who seems to know more than he tells, Lionel comes to discern that everything in the case is pointing toward Randolph and his powerful (and insidious) government agency, but there are still several questions remaining around him. For example, what is Randolph exactly trying to hide at any cost? Where did Frank hide what he found and then decided to use for blackmail? And, above all, how does Laura, who gradually becomes closer to Lionel along the story, fit in this very complicated picture?

Although it comes to lose some of its narrative momentum during its middle act, the movie keeps us engaged as having a number of various colorful figures popped out here and there around Lionel. While his three colleagues are depicted with each own personality, we get some amusement from a humorous scene between Lionel and Frank’s cynical widow, and there is also a slick jazz musician who happens to befriend Lionel and then comes to help him more than expected. As leisurely flowing from one offbeat character moment to another, the movie generates its own mood and rhythm, and that aspect is accentuated further by Daniel Pemberton’s score, which freely swings from jazz to electronic music for our extra entertainment.

Wisely not overplaying his character’s disability, Norton gives us an engaging noir hero we can care about, and he also assembles a bunch of talented performers around him. While Gugu Mbatha-Raw is effective in her intimate scenes with Norton, Alec Baldwin has a juicy fun with his evil and ruthless character as much as John Huston did in “Chinatown” (1974), and I certainly delighted to see other dependable performers in the film including Willem Dafoe, Cherry Jones, Bobby Cannavale, Leslie Mann, Ethan Suplee, and Michael K. Williams, who has been one of the most interesting character actors in our time since his breakout turn in HBO TV series “The Wire”.

On the whole, “Motherless Brooklyn”, which was a passion project for Norton for nearly 20 years, is not entirely without flaws, and I think it could be improved by shortening its rather long running time (144 minutes), but you may appreciate the admirable efforts from Norton and his cast and crew members. It is imperfect just like its hero, but the overall result is still as distinctive as other recent neo-noir films such as Paul Thomas Anderson’s “Inherent Vice” (2014), so I will not grumble for now.