In “Cracks,” a dark little tale directed by Jordan Scott (daughter of director Ridley Scott) and set in a girls’ boarding school in the English countryside, all is outwardly beautiful. And how! Lips in the film, which are usually pouting and receiving of loving close-ups, are deepest crimson; as sensuously undulate as the verdant hills in the background. The water in which the girls take their diving lessons is always sparkling, set in such a contrast to the gray stone of the school that it makes the harmony of colors sing. Everything is shot with a saturation of hue that deeply excites the eye.

But the aesthetic splendor proves, perhaps a little predictably, to be little more than a patina. The lips of schoolmistress Miss G (played with tense precision by Eva Green) are put to unspeakable use by their owners, and the shimmering water becomes the site of unhealthy competition amongst her students, as well as an ill-advised night of au naturel swimming. Not all is as lovely as it once seemed.

The performance of Green as the worshiped teacher and mentor carries this tension and gives weight to the disparity between the beautiful and the miserably ugly. Miss G acts the part of the charismatic leader, the model of enlightened womanhood to her girls, but the façade is never fully convincing. There is something lurking behind the smile. The keen observer knows from the beginning, owing to the tortured duality of Green’s acting, that Miss G is no Jean Brodie—she lacks that famous character’s intelligence, refinement, and life-experience. The shallow allure that Green conveys is not to be mistaken as depthless acting—it is the indeed the very crux of her character and the lynchpin of the film entire.

This surface beauty, communicated so effectively by Scott and her able team of actresses, and so essential to the film’s message, can nonetheless sometimes work against the film’s value as a piece of engaging cinema. One can easily tire of the brooding, plaintive gazes, and the zoomed-in, sped-up shot of a blooming flower in one scene is simply indulgent. Sometimes “Cracks” can feel like a watercolor painting; still and soft and lacking dashes of exuberant feeling.

Such lazy inertia, exemplified by a drawn-out pan of the pupils lying on the grass in sundresses on a summer day, is struck away with a vengeance, though, as “Cracks” turns nightmarish in its final act. Ultimately, the story is a sordid one. As the film ends, the plot veers onto such a wild, jolting track that the cheeks redden and the hand flies to cover the gaping mouth. But somehow, though “Cracks” turns out to be a nasty little shocker, it does not feel like trash. In the tradition of other British psychological dramas like 1992’s “Damage” and 2006’s “Notes on a Scandal,” the film is presented so artfully that we are not ashamed to take a perverse pleasure in its debased thrills. The filmmakers manage to give a gorgeous sparkle to their sleaze and delight the American viewer with their Britannic bag of tricks: lush landscapes, finely tuned turns of phrase, and pretty accents with elongated vowels.