Nearly a decade on from his last theatrical feature (2006’s “The Red Cockatoo”), prolific Teuton TV helmer Dominik Graf makes an overdue and very welcome return to the bigscreen with “Beloved Sisters,” an enthralling, gorgeously mounted depiction of the complicated relationship between the post-Enlightenment writer and philosopher Friedrich Schiller and the sisters Charlotte von Lengefeld (who would become his wife) and Caroline von Beulwitz (his eventual biographer). Retaining the novelistic narrative density offered by television while taking full advantage of cinema’s larger, more enveloping canvas, Graf has created an unusually intelligent costume drama of bold personalities torn between the stirrings of the heart and the logic of the mind, while casting his revealing gaze upon Western Europe’s bumpy transition from the 18th to 19th century. Premiered at Berlin in a 170-minute director’s cut, the pic is also being offered for sale in a 140-minute “theatrical” edit, though discerning fests and distributors should gravitate toward Graf’s preferred version.

As with the story of Charles Dickens and his mistress Nelly Ternan (the subject of Ralph Fiennes’ recent “The Invisible Woman”), the exact nature of Schiller’s relationship with the Lengefeld sisters has been the subject of considerable speculation and literary sleuthing, owing to the fact that Caroline destroyed nearly all her correspondence with the writer prior to her death, and remained mum on the subject of any personal entanglements in her 1830 Schiller bio. But Graf’s film sides with the view that Schiller maintained intimacies with both women at various times throughout their 20-year acquaintance — a physically and intellectually intense menage a trois that managed to withstand no shortage of shame, societal pressure and interpersonal recriminations.

The movie opens in Weimar in the fall of 1787, where the beautiful but somewhat awkward Charlotte (Henriette Confurius), called Lollo, has been dispatched to live with her godmother (the delightful Maja Maranow), an intimate of Goethe, to refine her ladylike ways and, hopefully, find a husband. These have been difficult years for the Lengefelds, who have fallen a few pegs in the social pecking order following the premature death of their aristocratic patriarch — a situation that Caroline (Hannah Herzsprung) has helped to remedy by entering into a loveless marriage with the wealthy but frigid courtier Friedrich von Beulwitz (Andreas Pietschmann). But Lollo, not least at her sister’s urging, has vowed to wait for true love to come along.

Admittedly, her first glimpse of Schiller (well played by Florian Stetter) is something less than auspicious, the frail young writer in threadbare coat stopping beneath her window to ask for directions. Though already a cause celebre on account of his 1782 play “The Robbers,” which was exalted and condemned in equal measure for its revolutionary politics, Schiller has achieved fame but no real wealth. Yet, the heart knows not of such things, and Lollo’s soon begins to flutter at each new mention of Schiller’s name. That bond intensifies during the summer of 1788, when Schiller vacations near the Lengefeld home in Rudolstadt, on the banks of the Saale River (where, in one harrowing scene, he nearly drowns trying to rescue a young girl).

With Von Beulwitz away on business, momentarily freeing Caroline from the shackles of marriage, the three enter into an intensely private world, exchanging passionate correspondence written in code and exalting in the rhapsodic natural beauty of Thuringian countryside. In the throes of this sun-drenched bliss, they resolve to share their lives together forever, though it is already clear that it is Caroline’s passion for Schiller that burns brightest (and vice versa). And it is that desire, alternately quenched and starved over the years, that becomes the emotional ballast of “Beloved Sisters,” through Schiller’s eventual marriage to Lollo, Caroline’s self-imposed four-year isolation from the couple, and her eventual reappearance, finally free of the husband who has burdened her life like an unwanted appendage.

Graf’s film is, on one level, a familiar tale of star-crossed lovers held apart by time, tide and the pestilent social climate of the era. But at every step, the filmmaker, who has an exceptionally acute sense of the relationship between the personal and the political, uses the push and pull of the characters as a window onto the unraveling social fabric of bourgeois European society. As revolutionary blood begins to spill in the streets of France, Schiller finds himself forced to reconsider his belief that “humanity will evolve through knowledge and the sight of true beauty.” And in scene after scene, Graf seamlessly inserts vivid details about a society in transition, from the modernization of printing techniques to the increase in literacy levels among the lower classes.

Graf isn’t an ostentatious stylist, but he stages marvelous setpieces, including a visit by Goethe to sleepy Rudolstadt that sets the whole town aflutter, and Schiller’s arrival at the U. of Jena, where he was appointed to a professorship in 1789. He’s also found a series of inspired devices for dramatizing the intensely passionate correspondence that flies back and forth between the characters with a speed that rivals today’s emails. (This is a movie deeply in love with quill ink and wax seals.) Above all, he’s made one of those relatively rare “period” films that pushes past the stuffy decorousness and mannerism of the dreaded “Masterpiece Theater” school to get at a highly plausible emotional and psychological reading of how people actually lived two centuries ago. (In this, and the airy, natural-light compositions of d.p. Michael Wieswig, the film calls Kubrick’s “Barry Lyndon” to mind.)

The film is rooted in two formidable performances. Herzsprung, who made a big impression as the prison inmate cum piano prodigy in “4 Minutes” (2006), is spellbinding here as the free-spirited Caroline, whose suppressed passions make her body quake with violent intensity when they are finally released. Relative newcomer Confurius, who owns two of the most penetrating blue eyes seen on a movie screen in quite some time, has a kind of glacial passivity as the woman who implicitly knows she is Schiller’s second choice — which makes it all the more startling when she finally comes undone.

Pic was shot primarily on real locations, carefully augmented by production designer Claus Jurgen Pfeiffer to achieve historical accuracy. Barbara Grupp’s striking but never unduly lavish costumes, and co-composers Sven Rossenbach and Florian Van Volxem’s vibrato string score, are other standouts of a topnotch tech package.