In Triple Frontier, a squad of retired special forces pals reunite for a mercenary raid on the South American fortress stash of a notorious drug lord, a premise that might have you thinking of Three Kings or even Kelly’s Heroes.

This movie, though, is a different animal. It’s written and directed by J.C. Chandor, known for his sophisticated looks at the complex intersection of ethics, power, and money, explored in Margin Call and A Most Violent Year.

He’s at it again with Triple Frontier — clearly less interested in the heist than its fraught aftermath, which dwells on the physical burden of hauling ill-gotten gains, and the harder-to-measure weight of guilt and regret.

Oscar Isaac, Chandor’s lead in A Most Violent Year, stars here as Pope, an ex-military hotshot now doing for-profit drug interdiction for an unnamed South American nation — the phrase triple frontier refers to the wild, sometimes lawless high-altitude borderland of Brazil, Paraguay, and Argentina.

Pope has targeted a reclusive narco kingpin who resides in a remote jungle compound, protected by his inaccessible location, and by corruption. Pope feels he can’t trust local law enforcement, and when he finally gets reliable information on the drug lord’s hideout, he decides to tell no one, returning to the States to recruit former colleagues, offering them a cut of whatever money they find once the “job” (the movie is honest enough to call it murder) is done.

It’s a hard sell. William (Sons of Anarchy’s Charlie Hunnam) believes in fighting only for country, and lectures active-duty soldiers against the temptation of for-profit, private-sector work. But he also sees that life after the military has been hard on buddies like Tom (Ben Affleck) and Catfish (Narcos’ Pedro Pascal), failed civilians who need money to support their hard-up families. A fifth man (Mudbound’s Garrett Hedlund) is the gung-ho, ready-for-anything part of the ensemble.

Chandor has a hard time injecting narrative tension into these putting-the-band-back-together scenes — always a dramatic challenge, because the outcome is preordained. More problematic is the way the characters are drawn. Traits that Chandor works hard to establish in the early scenes turn out to be inconsistent with the actions the men take once they reach South America.

Not ideal, especially for a movie that emphasizes character over action. You can feel that emphasis in the way Chandor stages the mountain raid — we’re primed for an action crescendo, but the scenes are almost matter-of-fact, as if the director is in a hurry to get to more important business.

And he is. The meat of the story can be found in the prolonged aftermath of the raid, when the men wrestle with the consequences of what they’ve done, and with the challenges of crossing the Andes (some impressive location shooting) and making their exodus. (Watching the men fight with bandits, and each other, it’s hard not to think of The Treasure of the Sierra Madre).

The movie opens with Hunnam’s character addressing a roomful of soldiers about the inevitable psychic cost of killing. Triple Frontier looks at how that cost is tallied when men kill not for country, but for money. Chandor’s script is adapted from a story by journalist/screenwriter Mark Boal (Zero Dark Thirty), and though it’s been many years in development, it remains a timely look at the dangers of our increasingly outsourced, privatized military-intelligence network.

‘Triple Frontier’

Directed by J.C. Chandor. With Oscar Isaac, Ben Affleck, Charlie Hunnam, Pedro Pascal, and Garrett Hedlund. Distributed by Netflix.

Running time: 2 hours, 5 mins.

Parents’ guide: R (violence)

Playing at: Ritz at the Bourse; Streaming on Netflix May 13.