Alicia Vikander is the titular “Firebrand,” starring as Katherine Parr, the sixth and final wife of Henry VIII. But the movie that reframes her legacy as a free-thinking and vengeful radical is only fitfully fiery itself.  

Jude Law actually steals the show as the corpulent and capricious king. Every time he’s on screen, director Karim Aïnouz’s film roars frighteningly to life. This ordinarily beautiful man subsumes himself to the grotesquerie, delivering a performance that’s at once hammy and terrifying.  

Otherwise, Aïnouz’s film, written by Henrietta and Jessica Ashworth and based on the historical fiction novel Queen’s Gambit by Elizabeth Fremantle, is too often a muted period drama. Much of that is by necessity: Katherine must remain stealthy in her pursuits of intellectual and religious freedom or risk befalling the same fate as the previous five wives. It is literally a matter of survival. Vikander is an actress of understated grace, but here, she rarely gets the opportunity to indicate her character’s inner turmoil. The eyes of the court are on her always, and spies are everywhere. 

This is especially true during a brief period in 1544, when Henry is off fighting in France and Katherine holds the temporary position of regent. She’d already been serving as a mother figure to Henry’s children from earlier marriages, Elizabeth (Junia Rees) and Edward (Patrick Buckley), the young heir to the throne. But now she must lead meetings about boring bureaucratic stuff with advisers who side-eye each other at her suggestions.  

Katherine also uses the opportunity to visit with a childhood friend who’s become a charismatic preacher: Anne Askew (Erin Doherty, hugely compelling in a brief role), who dares to have progressive notions about the church and be a woman at the same time. “Firebrand” truly sparks in this early scene, as we can see the charge of excitement running through Katherine’s body as she reconnects with someone who genuinely understands her, perhaps on multiple levels. The prospect of a romantic flirtation lingers in the thick forest air. 

But then it’s back to palace intrigue, full of whispers in dark corridors and hangers-on strenuously playing both sides. Chief among them is Eddie Marsan as Edward Seymour, uncle of Prince Edward through his late sister, Jane Seymour, Henry’s third wife. He and his brother, Thomas (Sam Riley), aim to remain in the volatile king’s good graces. There is also the undercooked suggestion that Katherine and Thomas may have had some kind of fling, which prompts the arrogant king’s jealousy. Mainly, these men are called upon here to mutter their manipulations beneath voluminous beards. Aïnouz rarely builds tension through these machinations; surprisingly, given what’s at stake, “Firebrand” is often a bit of a slog.