In 21 Bridges, Chadwick Boseman is a policeman so haunted by the memory of his own cop father's death in the line of duty that he's built his entire reputation around his itchy trigger finger. He's the "cop killer" killer, the guy the force calls in when they need someone to enact white-hot revenge and spare families from the agony of a trial — shoot first, don't ask questions at all.

You could see this being the launchpad for a thin-blue-line franchise in the 1980s, but it's a strange place to begin one in 2019. In light of all the renewed scrutiny on excessive use of police force in the last few years, can we still root for a mentality that frames the American city as a battleground between the good guys and the bad ones, free to shoot at each other with reckless abandon in the middle of the street? 21 Bridges is named for the number of exits there are out of Manhattan, and when it's time for Boseman's NYPD Officer Davis to track down two cop killers on the run in the dead of night, he orders all bridges sealed off until the sun comes up. "We flood the island with blue," he declares, which might be more bothersome if the film was pitched at a level more serious than "maybe you'll click on this on Hulu in two years."

The lockdown here is in response to two stickup artists (played by Stephan James and Taylor Kitsch) who kill seven officers in a botched cocaine robbery. A civilian dies, too, but no tears are shed for him — perhaps because he's in on the trade and therefore "no angel," as the local news would say. The bloodbath devastates the precinct captain (J.K. Simmons), who gives Davis and a protégé (Sienna Miller) carte blanche to bring them down. Seeing how quickly the law develops a thirst for blood is one of the film's more intriguing psychological aspects, though there turns out to be a simple explanation.

Once the gambit gets going, director Brian Kirk and screenwriters Matthew Michael Carnahan and Adam Mervis start throwing us some curveballs in the form of complex motivations for the killers. They're pawns in a larger game they can't see, one that will eventually push Davis to rethink his role as a glorified hired gun. Curveballs don't come, however, in the form of the actual city under siege; the blockades and street-level shootouts unfold without objection or even much interaction from New Yorkers. There's a sense of cheapness to many of the setpieces; at one point, a heavily fortified safehouse is quickly and easily stormed.

Boseman is an actor who seems more comfortable in an authority role, whether it's Black Panther or Thurgood Marshall, than he does as an antihero. Very little about his stoicism as a performer suggests someone who could ever be motivated to kill purely out of some misplaced sense of revenge. So it's hard to get a good read on his character in the early going, or at least what's motivating him before doubt sets in and he discovers the very T'Challa-esque brand of honor within him that compels him to hold his fire.

Here and elsewhere the film exhibits signs of a rushed edit job, particularly in a muddled backstory for Davis and the curious decision to cast Keith David, one of the best voices in Hollywood, in a role where he utters about two-and-a-half lines total. It's Stephan James, as one of the criminals on the run, who gets the standout role: as escape routes collapse around him, his soulful eyes (so piercing in If Beale Street Could Talk) give way to panic and regret. He refuses to let us see him as just another mugshot.

Unlike at least three other police-involved dramas this fall (Black and Blue,Netflix's American Son,and next week's Queen & Slim), 21 Bridgesisn't particularly interested in race. Nor does it present an entirely uncritical view of law enforcement. Lines are crossed, rights are violated, and people are killed. No one is let off the hook because they "get results," and in fact by the end, we may find ourselves questioning what "results" are supposed to look like. This makes for a fitfully enjoyable if somewhat workmanlike action flick. It's not really aspiring for brains, but still manages to pick up some on the hunt.

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