The worthy scouring of the past for hidden heroes, underrepresented figures and untapped dramatic potential has always kept historians and novelists dutifully occupied. One might think that England’s well-researched monarchs don’t belong in that category. But “Firebrand,” adapted from Elizabeth Fremantle’s novel “The Queen’s Gambit,” takes the position that Henry VIII’s final wife (of six), Katherine Parr, was more than just a devout, deferential nursemaid to an ailing king.

She was also a closet Reformist radical and, in one eye-opening tweak to established history, an abused spouse not to be messed with. Even if the facts don’t entirely support these notions, they’re not unappealing ones upon which to hang a portrait of a bad marriage at a turbulent time — despite the reality that Henry hardly requires outing as a serial #MeToo offender in need of comeuppance. And while it’s a tad surprising that Brazilian-Algerian art-house iconoclast Karim Aïnouz’s first English-language feature is a costume drama about English royals, it does sport two compelling stars in Alicia Vikander as protofeminist Katherine, and an almost unrecognizably heavy-set Jude Law as the Tudor tyrant.

That pairing, however, comes with drawbacks when the modernist screenplay (credited to Henrietta and Jessica Ashworth, along with Rosanne Flynn) meets Aïnouz’s meandering, atmosphere-thick approach. We drop in on Katherine in 1546 when she’s enjoying some interim power as n.