You should never judge a book by its cover, or in this case, a film by its title. From the sound of it, The Duke of Burgundy initially comes across like a stiff, historical bore, with perhaps a hint of mystery based off of its unusual and artistic poster. It doesn’t take long (in this case, just about five minutes) to come to the realization that this film is extremely provocative with nothing stiff about it, as we witness a relationship between two women engaging in private role-playing fantasies in this darkly sexual and artfully erotic film.

The film starts out with Cynthia (Sidse Babett Knudsen), a seemingly aristocratic woman, in her home surrounded by furniture made of dark wood, piles of worn books, and preserved butterflies. She is soon joined by Evelyn (Chiara D’Anna), a slightly younger woman whose role seems to be as one of Cynthia’s assistant/maid/gardener/and sexual companion. Yes, this isn’t a typical employer–employee relationship; rather, we are to discover this is a delicate and desired mistress–servant relationship. The sexual tension is quick to build, so we assume this isn’t the ladies’ first encounter, but we are left to wonder if this is a twisted, abusive relationship, or a giant role playing facade?

Over the course of the film, they incorporate lingerie, face-sitting, and bondage into their role-play, and the more physical it gets, the more we see Cynthia struggling with her relationship with Evelyn.

The existence of butterflies is a giant thread that runs throughout the film (the “Duke of Burgundy” quite literally being the name of a type of butterfly), the importance being that it is both ladies’ passions and areas of study. The beautiful creatures are displayed by the hundreds in Cynthia’s house- hung on thin pins in glass shadow boxes (one of Eveyln’s “chores” is to dust the delicate collection). An obvious, but true, correlation is the similarity between Cynthia and these butterflies; Both are strong, independent and beautiful, yet extremely fragile. Despite her tough outward demeanor as a sado-masochistic leader, Cynthia shows weakness and uncertainty in her eyes as their relationship gets more intense. Over the course of the film, they incorporate lingerie, face-sitting, and bondage into their role-play, and the more physical it gets, the more we see Cynthia struggling with her relationship with Evelyn. She is not happy, but her unhappiness unfazes Evelyn, who seemingly gets off even more by Cynthia’s nonchalance, ultimately leading to an emotional and physical breaking point.

Writer and director Peter Strickland certainly had a vision for The Duke of Burgundy, his keen eye towards building tension and holding suspense is successfully put to use here. Cinematically, the colors and texture of each scene act as a supporting character. It gives off a fantastically haunting vibe that mirror the characters on screen. The music, performed by Cat’s Eyes, sounds like a daydream of multi-instrumental, atmospheric pop similar to my favorite rock outfit, Beach House. All of the above give this film a stylized look that Andy Warhol would have been a fan of.

What makes The Duke of Burgundy so great is that the entire movie is a slow reveal; no piece of information is given away too quickly. We learn more about Cynthia and Evelyn as the film develops, making it extremely engaging and which keeps us excitedly guessing as to what will happen next. It is an erotic mystery drama, a genre that I believe Strickland created himself, and which he executes well. With the upcoming release of 50 Shades of Grey, audiences are becoming more open to the idea of seeing such a taboo subject on screen, but unlike 50 Shades, this outrageous S&M material is about two women disguised as proper and sophisticated lepidopterists whose groundbreaking and exploratory relationship makes for an unconventional piece of genre-bending film.

The Duke of Burgundy opens at Landmark’s Nuart Theatre in West LA and IFC Center in New York on Friday.