For a Downton Abbey enthusiast, The Chaperone, now in theaters in limited release, sounds almost too good to be true. The film is written by Downton creator Julian Fellowes; it’s directed by frequent Downton director Michael Engler. It’s set as the 1920s are just beginning to roar, which ensures to-die-for period sets and costumes. And, it stars none other than the Countess of Grantham herself, Elizabeth McGovern.

Alas, while it delivers all of the above as promised, this first foray into motion pictures by PBS and Masterpiece Theatre feels more like a made for television movie. It’s a bit too hushed and a bit too tame for the big screen. It’s certainly enjoyable — and quite beautiful to watch — but this particular historical drama could use a bit more . . . well . . . drama.

Based on the 2012 bestselling novel by Laura Moriarty, the film imagines a chapter from the pre-fame life of Louise Brooks, the real-life silent film “it girl,” who rose to fame as a daring icon of the jazz age. Brooks raised eyebrows for her progressive lifestyle and infamous bob hairdo (immediately copied by scores of U.S. shopgirls, not to mention Downton’s season five Lady Mary). In a 1979 profile, New Yorker critic Kenneth Tyson remembered Brooks as “the most seductive, sexual image of Woman ever committed to celluloid. She’s the only unrepentant hedonist, the only pure pleasure-seeker, I think I’ve ever known.” ‘Sounds like an exciting heroine, n’est-ce pas?

But, the film is called The Chaperone, not The Screen Siren.

The movie starts in 1922, a few short years before Brooks made her Hollywood debut in The Street of Forgotten Men. She’s an impatient teen, stuck in Wichita, Kansas, but longing for adventure. A naturally gifted dancer, she’s been offered a place in New York’s prestigious Denishawn School of Dancing and Related Arts. Her bohemian (and self-centered) mother is all for it, but her father refuses to let her go without a chaperone.

Enter Norma Carlisle, a middle-aged fixture of Wichita society, with a prominent attorney husband and two grown sons. Norma has her own reasons for wanting to leave, which reveal themselves later in the movie. She volunteers, and after a perfunctory interview — and despite Mr. Carlisle’s displeasure — this odd couple is on a train en route to the big city. Louise is eager, outspoken, and a bit too worldly for her own good. Norma is conservative, conventional, and tight-laced. Literally. To Louise’s amusement, the reed-thin chaperone still wears a corset.

The two are at odds almost immediately. Louise is a flirt, sitting with strange men in the club car and charming a taxi driver to take them uptown even though his shift is ending. Norma attempts to instruct her. “Men don’t like candy that’s been unwrapped,” she warns. “It might be clean, but they don’t know where it’s been.” Suffice it to say, Norma is going to have her hands full.

Fortunately, once they arrive, Louise is safe and sound at Denishawn’s at least part of each day. This gives Norma time to pursue her own education. It turns out that she was born and spent her first few years in New York, a student at the downtown Home for Friendless Girls, before being taken out west on an orphan train and adopted by a Kansas farming family. Norma hopes that the nuns at the orphanage can shed some light on her background.

“I want to know who I am,” she pleads with the mother superior.

“You’re a child of God,” she’s told.

Norma befriends widower Joseph, a gallant German handyman, who has a young daughter living at the orphanage. After some hesitation, Norma convinces him to help her steal her records while the nuns and their charges are at mass. She finds a letter from “a friend of the birth mother,” and writes to the woman, hoping she’ll come from Massachusetts to meet with her.

She soon needs Joseph’s help again to rescue Louise from a seedy speakeasy. The unrepentant teen, surrounded by men and downing cocktails, breathes in Norma’s face. “Do you like that, Norma?” she sneers, “It’s gin, gin! That’s what it is.” Later, she allows Norma to help as she experiences the sickening effects of so much “gin, gin.”

Louise, whose sensual, modern dancing really is spellbinding, is invited to dance with the company in Pennsylvania. This gives Norma time for a heartbreaking meeting with the woman from Massachusetts and a romantic night with Joseph. The two are seen and Joseph loses his job. Meanwhile, Louise is offered a permanent position with Denishawn (Ted Shawn is delighted; his wife, Ruth St. Denis, is jealous), and will be staying in New York. Without revealing too many plot twists, suffice it to say that Norma returns to Kansas and creates a non-traditional family that, while dramatically satisfying, might be more plausible in the 2020s than the 1920s. The movie ends twenty years later, when a much wiser Norma offers advice to a disillusioned Louise, urging the younger woman not to give up on her dreams. Their roles have reversed and now Norma is the one who can imagine a happy ending.