(CNN) - Like the breakup itself, "Brexit" starts out a little messy, and before it's over, leaves behind an unsettling, queasy feeling regarding the political referendum that roiled Europe, without sparing America from its nefarious implications and striking parallels.
"Everyone knows who won. But not everyone knows how," the movie -- a collaboration of HBO and the BBC -- notes at the outset, before segueing to the campaign over whether Britain should exit the European Union, and the shadowy forces that were enlisted, or perhaps more accurately unleashed, which helped carry the day.
The seemingly ubiquitous Benedict Cumberbatch stars as Dominic Cummings, a political "attack dog" chosen to spearhead the "Vote Leave" effort. Cummings insists on "total autonomy," despite the various Conservative Party and right-wing populist UK Independence Party (UKIP) representatives seeking to influence the decision-making, with whom he repeatedly clashes over strategy.
Leaving virtually no one completely unscathed, the film includes depictions of Boris Johnson (Richard Goulding) and Nigel Farage (Paul Ryan) -- two high-profile British politicians -- that make them look largely like oafish clowns.
Cummings, meanwhile, engages the mysterious research firm Cambridge Analytica, whose technology has found a way to identify "invisible" voters, making the polling being relied upon by the rival Remain campaign -- run by Craig Oliver (Rory Kinnear), then-Prime Minister David Cameron's director of communications -- largely irrelevant.
It's all a bit dizzying in the early going (perhaps more so to an American audience), even with helpful chyrons to introduce and identify the key players. Stay with it, though, and "Brexit" conjures a sobering look at the corrosive effect of "little wells of resentment" that were assiduously filled and replenished for decades, nurturing the hostility that erupted first in the UK and then, with the election of Donald Trump, in the US.
Even knowing the outcome, the glimpses behind the curtains of the two campaigns -- as written by James Graham, and directed by Toby Haynes -- presents a fascinating chess match. What tilts the board, it's made clear, is that Cummings not only comes to the battle armed with secret data but also allies who eagerly use brazen lies to set the terms of the debate.
The most sobering conversation occurs near the end, during a somewhat overly on-the-nose exchange between Cummings and Oliver, calmly debating the possible repercussions from what the referendum hath wrought -- the byproduct, as Oliver puts it, of "a slow drip, drip, drip of fear and hate."
Cumberbatch is, as always, crazy good, investing his unflattering role with a wild-eyed energy and quick wit -- portraying Cummings as a guy with marginal people skills but a keen mind for locating an opponent's weakness.
Any movie made this close to the actual events is going to brave criticism over the creative liberties taken in condensing a complex story into 90 minutes, especially when the latest chapter in Brexit's fallout -- and the chaos associated with it -- is currently being written. But "Brexit" zeroes in on the bigger picture -- the consequences of which are still rippling through western society -- and the deep-seated discontent that the Leave campaign, however unsavory its methods, transformed into a stunning victory with a long, consequential tail.
"Brexit" will air Jan. 19 at 9 p.m. on HBO.
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