starstarstar-halfstar-outline(2.5 stars)

When the book “Guantánamo Diary” came out in 2015, the controversy over the detention of terrorist suspects in the U.S. military prison on the coast of Cuba had already been raging for 12 years. And the author of that best-selling memoir, Mohamedou Ould Slahi, had been imprisoned there for 13. Slahi wouldn’t be released until October 2016, after serving 14 years without ever being formally charged.

And so the arrival of “The Mauritanian,” the buzzy new prestige drama by Oscar-winning director Kevin Macdonald (“One Day in September”), based on Slahi’s book, comes nearly two decades after the arrest of Slahi that opens the film. (He was taken into custody by police in his homeland of Mauritania on Nov. 20, 2001, on suspicion of helping to recruit the 9/11 hijackers for al-Qaeda.) In the interim, there have been a slew of documentaries about the mistreatment and torture of Guantánamo detainees, the most notable of which was Alex Gibney’s Oscar-winning 2007 exposé “Taxi to the Dark Side.”

All which saddles “The Mauritanian” with an unfortunate burden that might be called outrage fatigue. Despite a powerful performance by Tahar Rahim in the title role, and despite such marquee names as Jodie Foster and Benedict Cumberbatch in the supporting roles of Slahi’s attorney, Nancy Hollander, and Stu Couch, the Marine lawyer assigned to prosecute him — despite scenes of grotesque abuse that inflame the conscience — the movie lands, through no fault of its own other than timing, with a whiff of been-there, done-that.

The year 2020 was a dumpster fire of indignation over the mishandling of the pandemic response, racial injustice and unfounded claims of widespread fraud in the presidential election that have deepened the open wounds of political division. Is it any wonder then that it’s hard to muster even more anger about something that feels like we’ve been screaming about for two decades?

That no criticism of Rahim, who delivers a memorable and intense performance, bringing a sense of wit and humor that is, at times, hard to fathom for one so mistreated. The actor generates sympathy for his character, even considering the ambiguity, for much of the narrative, about his guilt. (Slahi had confessed, but also passed a lie-detector test after he recanted.) Foster and Cumberbatch leave a less indelible impression, playing characters who come across, in the case of the former, as more brittle and testy than morally resolute, and, in the case of the latter — a prosecutor who balked at using a confession he believed was tainted, inadmissibly, by torture — as more sanctimonious than saintly.

The battle between Hollander and Couch — a battle that paints them, eventually, as adversaries-turned-unlikely-allies — is, in any case, hardly the point. “The Mauritanian” is no courtroom drama. If it were fiction and not fact, it might have benefited from the familiar trajectory of a legal thriller, culminating in a surprise verdict vindicating the righteous.

But that’s not the way things happened. Most of the movie’s running time takes us only up to the 2010 decision in Slahi’s habeas corpus petition, challenging the basis of his detention. There’s another six years of story to be told: a telling that is dispensed within an epilogue of anticlimactic on-screen titles, followed by a few short clips of the real Slahi.

Those documentary clips present a jovial man who seems oddly free from bitterness. Even more paradoxically, they deliver more far more questions than the film that comes before them.

R. At area theaters. Contains violence, including a sexual assault, and crude language. 129 minutes.