Saoirse Ronan on fire as smart but rash Mary in ‘Queen of Scots’

One sign of a great performer is her ability to burn brightly in a bad movie. Saoirse Ronan dazzled in “Atonement,” but I knew she was brilliant when I saw her in Peter Jackson’s disastrous adaptation of “The Lovely Bones.”

That movie never clicks, yet Ronan is spellbinding in it. Now, coming off strong work in “Lady Bird” and “Brooklyn,” the Irish actress is again on fire in a movie that isn’t up to her level.

“Mary Queen of Scots” is no dud of “Lovely Bones” proportions, thankfully — merely a mediocre history lesson. The film is the umpteenth take on British royal skullduggery, this time opening in 1561 and focusing on the title character, played by Ronan, and her cousin, Queen Elizabeth I (Margot Robbie). Mary is Scottish and Catholic, Elizabeth is English and Protestant. They are extremely wary of each other.

The script, by “House of Cards” creator Beau Willimon, includes juicy historical tidbits: Elizabeth’s maneuver to offer her own Friend With Benefits and court fave Robert Dudley (Joe Alwyn) to Scotland as a potential husband for Mary, and Mary’s snub of Dudley in favor of marriage to the questionable Lord Darnley (Jack Lowden).

Director Josie Rourke (a stage veteran making her film debut) suggests that the women had more in common than not. Both are surrounded by conniving men who seem to hold the real power, despite Elizabeth and Mary’s official regal status.

The fine actors who play the advisers include Guy Pearce, Ian Hart and the deft Adrian Lester (the film does the colorblind casting thing, so black actors like Lester are part of the royal court). Especially creepy is David Tennant’s turn as the Protestant leader John Knox, whose misogynistic tirades against Mary all but end with his faithful chanting, “Lock her up!” (They actually chant “Kill the whore!”, but the filmmakers make sure we get the parallels.)

There’s appeal in this kind of historical pageant, which is why the story has been depicted so many times, including a 1971 film of the same title, with Vanessa Redgrave as Mary and Glenda Jackson as Elizabeth. As anything other than an actors’ showcase, though, this “Mary” has a tendency to plod along.

Kudos to Margot Robbie in her ongoing quest to be the shape-shifting Bette Davis of our time; after “I, Tonya” and “Suicide Squad,” she’s still in character actor mode, wearing hideous wigs and letting her makeup show the scarring signs of Elizabeth’s bout with smallpox.

She’s got a decidedly supporting role, as Ronan’s Mary occupies center stage. The actress blazes through this characterization, showing us Mary’s strategic intelligence as well as her sometimes ill-fated rashness.

The film does some speculating, including a scene with the two queens meeting in person. It’s a tantalizing moment: What if the royals had buried their differences and put together a 16th-century dream team? Maybe the feminist cause would’ve had a 400-year head start, instead of having this chapter end in another bloody royal beheading.

“Mary Queen of Scots” (2½ stars)

A well-acted if plodding account of the rivalry between the Scottish Catholic Mary (Saoirse Ronan) and the English Protestant Elizabeth (Margot Robbie) in the 16th century. The film makes some parallels with current events, but its biggest draw is Ronan’s blazing performance as the smart but rash Mary.

Rating: R, for violence

Opening: xxxx