“Firebrand” is the first English-language film by Brazilian-Algerian director Karim Aïnouz, and he infuses this portrait of mid-1500s Tudor England figure Katherine Parr with an entrancing fluidity with which you cannot help but be impressed.

In theaters this week, “Firebrand” also benefits from an understated performance by Alicia Vikander, as the English queen and regent and a bolder turn by Jude Law as her tyrannical husband, King Henry VIII.

In all, though, this adaptation of Elizabeth Fremantle’s 2012 historical novel, “The Queen’s Gambit,” feels like at least a slight missed opportunity, a tale that instead of building momentum to its climax loses a bit of narrative momentum in its third act, even as the stakes for Katherine are of the life-or-death variety.

In his director’s statement, Aïnouz — whose credits include “Invisible Life,” “Mariner of the Mountains” and the documentary “Central Airport THF” — talks of “reimagining of a ‘period’ film, closer to a psychological horror film, or a political thriller,” which is how “Firebrand” plays. (Later in the film production notes, it is stated he is not a fan of the term “biopic,” and so what we get here is but a sketch of a brief time in its main subject’s life.)

Parr was the sixth and final wife of Henry VIII — in recent years, she, Catherine of Aragon, Anne Boleyn, Jane Seymour, Anne of Cleves and Catherine Howard have been the heroines of the award-winning stage musical “SIX” — and early on in “Firebrand,” Katherine seems to believe she can influence Henry for the betterment of England. She says as much to old friend Anne Askew (Erin Doherty of “The Crown”), who is making waves in the countryside a Protestant preacher, aka “a radical.”

After all, Henry has appointed Katherine regent as he’s gone off to war, she points out to Anne, with whom she secretly meets.

“He puts a woman on the throne so a man cannot take it while he’s gone,” Anne counters.

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(Opening on-screen text also reminds us that “history tells us a few things, largely about men and war.”)

Thus, it is not surprising that when Henry arrives home — earlier than expected, as a worsening leg condition made it embarrassingly difficult for him to mount his horse in front of his men — he pushes her aside, along with her concerns about the plague and the the possibility of revolution.

“I’m home,” he says, “and you don’t need to worry your head about it anymore.”

As “Firebrand” progresses, however, Katherine will need to worry about her head, literally, as Henry grows suspicious of her for one potentially life-threatening reason or another. Fortunately for her, she becomes pregnant with his child, which, of course, he hopes to be a son.

Jude Law, left, and Alicia Vikander in “Firebrand.” (MBK Productions/Zuma Press/TNS)

Katherine is painted as a loving mother to Henry’s three existing children, all the products of previous wives, and is especially adored by Princess Elizabeth (Junia Rees), who, down the line a bit, will rule England and Ireland for nearly 50 years as Elizabeth I. They certainly are closer to her than to their biological father.

Vikander, an Academy Award winner for her work in 2015’s “The Danish Girl” whose credits also include terrific performances in “Ex Machina” and “The Light Between Oceans,” seems determined to give a less-is-more performance here. It’s fine work, but “Firebrand” may have benefited from a, well, more fiery moment or two from Katherine, who is, understandably, increasingly preoccupied with her mere survival.

No such concerns with the work of the similarly skilled Law (“The Talented Mr. Ripley,” “Fantastic Beasts: The Secrets of Dumbledore”), whose moments of intensity are responsible for much of the film’s tension. Henry is a man to be feared, greatly, even as his health worsens.

While Law reportedly wore weights under his baggy royal garb to convey the growing size of this ruler with a big appetite, more noteworthy is that he found someone to create on-set scents to help sell the idea that the “filth and rotting of his body” were creating horrible odors, according to the film’s press notes.

‘You can see people having a visceral reaction to the environment — that is something that really helped in terms of the performances,” says producer Gaby Tana.

Jude Law, left, portrays English King Henry VIII in “Firebrand.” (MBK Productions/Zuma Press/TNS)

As we can’t actually smell the movie even in the most technologically advanced cineplexes, we are left with the aforementioned acting and direction, along with the screenplay by sisters Henrietta and Jessica Ashworth (“Tell It to the Bees”), with “additional writing” by Rosanne Flynn (“Military Wives”). Like the other elements, the writing boasts more good than bad but is unremarkable.

“Firebrand” also benefits — if only so much — from solid supporting onscreen work by Simon Russell Beale, as politicking Catholic bishop Stephen Gardiner, and Eddie Marsan and Sam Riley, as brothers Edward and Thomas Seymour, respectively, who are noblemen and allies of Katherine,

Parr, who also is referred to as Catherine and Kateryn in writing, was said to have been vivacious and witty, and we get a glimpse of that in a well-executed scene in which Henry insists Katherine be the person to test his food to ensure it hasn’t been poisened. Her handling of this tense situation provides the film with one of its finest moments.

It’s also an example of how a decent film could have been stronger with a few choices having been made differently.

‘Firebrand’

Where: Theaters.

When: June 14.

Rated: R for some violent content, brief gore and sexuality/nudity.

Runtime: 2 hours.

Stars (of four): 2.5.