You probably don’t know the name Greville Wynne, but the British businessman-turned-spy is at least partly responsible for putting the kibosh on what very well could have been the end of the world during the Cold War.

Benedict Cumberbatch plays Wynn in The Courier, a new docu-drama that delves into Wynne’s contributions to British intelligence’s leaking of documents proving Russia had installed nukes in Cuba during the Kennedy/Khrushchev standoff. The real-life Wynne was sent by England’s MI6 (like their CIA) to warn deep-seated Russian asset Oleg Penkovsky about impending dangers. Fearing for his family, Penkovsky signaled the Brits about Khrushchev’s desire for confrontation circa 1960 and, working with Wynne over a few years, the pair was able to steal and leak classified information that tipped the scales in America’s favor. War, as we know, was averted, and the rest is history.

Cumberbatch proves as capable as always in his quest to play every British history-maker ever (even if his performance as Alan Turing in 2014′s The Imitation Game felt more inspired). Here as Wynne, Cumberbatch’s take on terrified-yet-resolute is palpable, but Merab Ninidze as Penkovsky is the real winner of the film. Even borderline hackneyed speeches about two people being the start of change feel moving with Ninidze’s stoic delivery, and as the truth of his risks unfold, we learn why Wynne was so willing to risk his own life in reciprocity.

Elsewhere in the film, Ms. Maisel star Rachel Brosnahan provides a serviceable turn as the American CIA agent Emily Donovan, whose efforts to protect both Wynne and Penkovsky makes the ultimate fallout of Khrushchev’s—and indeed Russia’s—paranoia feel all the more heartbreaking. Scenes with Wynne’s family (played by Fargo’s Jessie Buckley and some fucking kid) feel tacked on, or at least like semi-hollow attempts at adding drama; it kind of stings that Buckley’s turn as Sheila Wynne at worst amounts to little more than an obstacle in the grand scheme of things and, at best, an offscreen motivator.

No spoilers here, though the true history is readily available online, but The Courier may best be described as harrowing and a bit tedious. Yes, it’s fascinating and perhaps a lesser-known chapter in international history—but it’s not the nonstop thriller its trailer would have us believe.

7

+Amazing history; Merab Ninidze slays

-Supporting roles are boring; tedious final act

The Courier

Directed by Dominic Cooke

With Cumberbatch, Ninidze, Brosnahan, Buckley and some fucking kid

VoD, PG-13, 112 min.