Sally Hawkins, front left, and Harry Lloyd, on horseback, in “The Lost King.” Graeme Hunter/Courtesy of IFC Fi

“The Lost King” gets off to a pacey, involving start, with the help of a slashing, gestural musical score reminiscent of Bernard Herrmann at his Hitchcockian best.

The rest of “The Lost King” might not live up to that initial urgency, but it takes on its own gentle momentum. Sally Hawkins plays Philippa Langley, a sort-of-single mother of two (more on that later) living in Edinburgh who becomes obsessed with Richard III, the English king who, thanks to Shakespeare’s play bearing his name, will forever be known as the hunchbacked schemer who had his nephews killed to claim the throne.

Well, maybe not forever. “The Lost King” recounts how Langley spearheaded a campaign to find and exhume Richard’s remains, an effort that came to fruition in 2012 in a Leicester parking lot. Directed by Stephen Frears (“Philomena”) from a script by Steve Coogan and Jeff Pope – and based on Langley’s memoir of the event – “The Lost King” obeys the contours of the classic underdog story, in this case about an unassuming woman who defies credentialed authorities, pompous skeptics, her own insecurities and Shakespeare himself to literally dig up a truth that has been distorted and erased for centuries.

Despite Frears’s most energetic attempts to infuse suspense into the material (including hiring Alexandre Desplat to write that terrific Herrmann-ian music), it can’t be said that “The Lost King” is anything but predictable. But its pleasures and compensations lie not in plotty complications or some third-act twist, but in the humanity that suffuses an enterprise that is borne of obsession but achieves a form of transcendence.

Sally Hawkins in “The Lost King.” Graeme Hunter/Courtesy of IFC Fi

Hawkins plays Langley – who can be glimpsed in one of the film’s final scenes, during Richard’s reburial – as a harried, somewhat hollowed-out character. As in real life, she suffers from chronic fatigue, and because of that, and a fragile demeanor, she’s constantly underestimated. But throughout “The Lost King,” Philippa is also a fighter, whether it’s for a better job at the office or pursuing justice for a man who, she increasingly comes to believe, was slandered in the name of revisionist Tudor propaganda.

She’s also juggling an untraditional home life: She and her husband, John, portrayed in a mordantly sympathetic performance by Coogan, are separated but clearly still love each other, and he (mostly) unquestioningly takes on the care of their two teenage sons while she attends meetings of the local Ricardian society and lobbies the University of Leicester for archaeological support. One of the strengths of “The Lost King” is that the filmmakers let Phillipa and John be: No tearful reunions or melodramatic fights here, just the daily business of making a family work, in the most healthy and loving way one knows how. (Another strength is the full advantage Frears takes of fabulous locations in Edinburgh and Leicester.)

That low-key embrace of difference extends to Philippa’s mystical connection to Richard, personified by the wonderful Harry Lloyd in magical-realist scenes of spiritual communion. Reportedly, the real-life Langley really was driven by an almost psychic sense of where she would ultimately find Richard – up to and including the letter “R” appearing at an opportune moment. Rather than fuzzy-wuzzy sentimentalism, that liminal space between objective reality and the netherworld is presented as a natural, if exceedingly rare, fact of life.

Ultimately, “The Lost King” centers on Plantagenet-worthy politics, when the bigwigs at the University of Leicester try to elbow Philippa out of her due credit for finding Richard’s remains. (Unsurprisingly, that fight was rekindled with the U.K. release of the film.) With Hawkins’s alternately elfin and flinty performance at its center, “The Lost King” winds up being a paean to amateurism and unconventionality. Greatness comes in all shapes, sizes and packages; genius can take any number of forms. Hidden depths are everywhere. You just have to know where to look, and do a little digging.