As the subtitle suggests, “Queen Charlotte: A Bridgerton Story” is a prequel and spinoff to the hit Netflix series, which adapts Julia Quinn’s Regency Era romance novels with the soapy, progressive sensibility of producer Shonda Rhimes. In practice, though, the six-episode series is more like “Bridgerton” Season 2.5. Though the story flashes back some 50 years to depict the titular monarch’s early marriage, it keeps the flagship show’s stylistic trademarks firmly in place, from the classical covers of contemporary pop songs to the voiceover by Julie Andrews’ Lady Whistledown. There’s even a timeline set just after the most recent season centering the social set’s elder stateswomen: Lady Danbury (Adjoa Andoh), Violet Bridgerton (Ruth Gemmell), and Queen Charlotte herself (Golda Rosheuvel).

“Queen Charlotte” is not a break from precedent. Instead, it’s a return to form for Rhimes, who serves as showrunner in her most hands-on role since “Inventing Anna,” a disappointing — if hugely popular — take on the Anna Delvey saga. Rhimes had previously delegated “Bridgerton” to creator Chris Van Dusen and writer Jess Brownell, who takes the reins for the upcoming Season 3. But in the hands of the master who gave us “Grey’s Anatomy” and “Scandal,” the “Bridgerton” universe becomes the best version of itself: a sexy, escapist love story with a maturity and substance that only adds to its eroticism. “Bridgerton” was already a phenomenon. It still takes “Queen Charlotte” to unlock the premise’s full potential.

In Season 1, “Bridgerton” made its mark with explicit, athletic sex (no ABC censors here!) and an alternate history of England in which the aristocracy is racially integrated. These elements were so attention-grabbing they partly overshadowed the central relationship, a pleasant-enough pairing of two beautiful people. In Season 2, “Bridgerton” backtracked a bit, dialing way down on the nudity while also crafting a rich, yearning romance that put its characters first. “Queen Charlotte” ends up with the best of both worlds. The union of a 17-year-old Charlotte (India Amarteifio) and a freshly crowned King George III (Corey Mylchreest) — yes, that King George — occurs in the premiere, opening the door for all that comes after courtship, both emotional and physical. Their marriage ends up touching on matters of race, mental health, bodily autonomy and, eventually, the meaning of desire and long-term partnership past middle age, all issues treated with due gravity without killing the fantasy. 

It’s a narrow line to walk. Charlotte’s arrival in England occasions what courtiers deem “the Great Experiment”: the sudden, dramatic bestowal of titles, lands and privileges on select people of color. As with all previous attempts to explain exactly how race works on “Bridgerton,” every detail prompts as many questions as it answers. The actual Queen Charlotte, some historians believe, may have had some African ancestry, which here leads her future mother-in-law Princess Augusta (Michelle Fairley) to make comments about Charlotte’s skin tone clearly inspired by real-life royal drama. But Augusta quickly resolves to remake the nobility in her new family member’s image, though it’s unclear exactly how they’re selected or from what pool of candidates. There’s some resistance from the old guard, though it’s never explicitly racist, again begging some follow-ups about the preexisting status quo.

Inquiring minds will be appeased by the chemistry between Amarteifio and Mylchreest, built through a more interesting conflict than the typical will-they-won’t-they. The question is not if these two will get together, but how they’ll navigate the inevitable obstacles now that they’re bonded for life. Shows like “Catastrophe” have explored this idea in the modern day; “Queen Charlotte” takes unrelatable opulence and infuses it with emotion, even as there’s plenty of eye candy. George struggles with what we’d now call mental illness, and was then deemed fits of madness. His shame, her indignation at being shut out and their palpable attraction power a roller coaster we can instantly invest in.

The Queen Charlotte of “Bridgerton” is a peripheral presence, only descending from her royal perch to issue proclamations and make cutting remarks in over-the-top outfits, to viewers’ delight. On a weaker show, our knowledge of how her life turns out would sap a prequel of suspense, or worse yet, dilute the impact of Rosheuvel’s fabulously regal performance. Instead, Amarteifio credibly finds the roots of Charlotte’s willful, self-centered, sometimes petulant charm in her teenage self. (After all, that combination of traits is normal in any teen girl, whether or not she’s a queen.) Rosheuvel’s role underscores the continuity between the two actors while also giving adult Charlotte her first real subplot as she pressures her 15 children to produce a legitimate heir.

In its brevity, “Queen Charlotte” can strip down the broad ensemble of “Bridgerton” into a more focused story. The show still makes room for supporting parts like Charlotte’s footman Brimsley (Sam Clemmett), who’s engaged in an illicit affair of his own, and a young Agatha Danbury (Arsema Thomas), not yet a lady and in a loveless marriage to a wealthy older man. Thomas is a standout, and her character’s journey leads to a conclusion that might as well be sacrilege in the marriage-obsessed “Bridgerton” milieu: that happiness can be found and defined outside the context of enduring matrimony. 

The “Bridgerton” project is, at its core, to give a conservative genre a reformist sheen while keeping the underlying structures intact. (This is a show that can make Americans root for the very man we declared independence from, give or take some casual mentions of the colonies.) Whether or not you approve of that aim, “Queen Charlotte” is as close to a flawless execution as its franchise has gotten yet. Netflix is eager to expand some of its biggest homegrown hits — “Stranger Things,” “Squid Game,” and yes, “Bridgerton” — into full-blown universes. But in its clear understanding of what makes “Bridgerton” work, and where it can improve, “Queen Charlotte” feels organic rather than cynical. 

It also offers an ideal metaphor for what the best spinoffs can do. In a scene that epitomizes the show’s frothy, often funny, insightful tone, Violet and Agatha euphemistically refer to their libidos as a “garden”: something that can go dormant or grow lush, depending on the season. “Everyone has a garden,” Agatha says, an objective truth and a statement of purpose. Anyone can love and be loved, and so anyone can star in a love story. “Bridgerton” is already a more inclusive romance than most, but even its seasons end with the birth of a baby or a walk down the aisle. “Queen Charlotte” keeps going, and suggests “Bridgerton” could, too.

“Queen Charlotte” premieres on Netflix on May 4.