No festival film this year has attracted as much buzz as Regina King’s directorial debut. Her collaboration with Kemp Powers (they have expanded his 2013 stage play) cost just $19.6 million, yet is already being talked up as a ground-breaking awards contender.

Should you believe the hype? Yep, King’s the greatest.

In 1964, Cassius Clay (Eli Goree) celebrates his win over Sonny Liston by going to a motel with Sam Cooke, Jim Brown and Malcolm X (Leslie Odom Jr, Aldis Hodge and Kingsley Ben-Adir). The latter is in a bind — he wants to leave the Nation of Islam but knows this could beggar him financially, and possibly cost him his life.

X’s careworn intensity is brilliantly conveyed by Londoner Ben-Adir. When Brits play Americans, it can ruffle feathers. How brave of King to simply pick the best man for the job.

The bulk of the film is set in the motel. Will they just talk all night? What’s so clever about the writing is that Cooke and Brown get antsy for us, from the minute they see the motel’s dingy four walls. These two strong personalities are obviously not in the mood for jaw-jaw. They fret, so we don’t have to.

Over the course of the evening, the friends often treat each other like foes. There’s spry banter about everything from Bob Dylan to pork chops, but also scalding debate, especially between X and Cooke. The ideas exchanged are electrifying. And all the leads are sublime. Still, casting the Hamilton star Odom Jr was the masterstroke. Every time he sings (and he sings a lot) we’re putty in his hands.

We don’t need Goree/Hodge/Ben-Adir to be brilliant at boxing/football/thinking; it’s enough that they’re brilliant at acting. What a bonus, though, that Odom Jr actually IS what he’s pretending to be, a man with a superhuman voice. All four deserve Oscars, but if I had to choose, either Odom Jr or Ben-Adir would get my vote.

The sense that X is living on borrowed time adds a terrible urgency to the proceedings (Lance Reddick does sterling work as Kareem, a sour henchman for the Nation of Islam; he’s got his eyes on X and his gaze isn’t friendly). It’s hard, after watching this, not to ask yourself “what if?” As in, what if Clay, AKA Muhammad Ali, soon to join the Nation of Islam, had sided with X, instead of the movement’s corrupt leader, Elijah Muhammad? That said, King doesn’t make the mistake of casting Muhammad as the villain. From first to last, insidious, institutional, racism is the enemy.

One Night in Miami could have felt like four biopics of 20th century icons stuffed into one. It’s more like a protest march-cum-party. The biggest problem with it is that the evening’s over too soon.