Eileen lives in a beige world. When she’s not staring out the window of the drab prison office where she’s employed as an office drone, curiously transfixed by the new inmate who murdered his father, or taking care of her alcoholic WWII vet father, she’s practically drowning in the grays and browns and mustard yellows of her 1960s seaside New England town. So when a pop of color arrives in the form of a noticeably red sedan that pulls into the prison parking lot, she’s instantly curious. But when she sees that the driver of the sedan is blonde bombshell Dr. Rebecca St. John, the prison’s new psychologist, she becomes so transfixed that she may never be the same.

Obsession can be a solid way to start a drama, and can lead to any number of exciting outcomes. Eileen, the new film from director William Oldroyd, begins as a fairly straightforward character study before a decidedly sharp turn into a thriller in the third act. Based on the novel by Ottessa Moshfegh, who serves as co-screenwriter with Luke Goebel, the film presents as a kind of interesting cinematic experiment in tones, but doesn’t fully coalesce into a complete whole.

What the film lacks in cohesion, it makes up for in the performances of its two leads. Thomasin McKenzie, who plays Eileen, has made a career out of playing mousy uncertainty. In her hands, Eileen is simply trying to get by, dealing with drunken outbursts from her father, and all of life’s various unpleasantries. She’s prone to shocking fantasies and daydreams, usually revolving around murder or sex. The film opens with her observing a pair of backseat lovers from her own car.

Hathaway leans into her inherent sex appeal, making Rebecca an intoxicating presence for Eileen – and not just because she’s more exquisitely put together than those she’s surrounded by. There’s an element of mystery surrounding her: she comes from New York, has a kind of Mid-Atlantic Katherine Hepburn accent, and she’s purposefully vague about her previous life. She wields her sexuality like a knife, and one of the film’s lingering mysteries is how much Rebecca uses that to entice Eileen for her own gains. The bulk of the second act of Eileen feels like a riff on Todd Haynes’ Carol, where Eileen feels an unspoken attraction to Rebecca. McKinzie and Hathaway’s chemistry together is electric, and helps to sell the hard left turn of the third act.

Make no mistake, the final piece of the film is thrilling and intriguing, but it almost comes out of nowhere, almost feeling like it came from a different film entirely. It’s difficult to discuss without spoiling the fun, but it’s the kind of swerve that almost feels earned. There’s an undercurrent throughout Eileen of its protagonist seeking an exciting escape from her ho-hum life, which Rebecca provides in the film’s finale. Something dark has been lurking beneath the surface of Eileen, and Rebecca unleashes it in unexpected ways. The final moments feel like a bit of a shrug at first, but the implications have lingered with me long after finishing the film.

Oldroyd at least has the good sense to not overstuff the narrative. At 98 minutes, Eileen gets in and out without heavily underlining what it’s doing. Maybe that’s a benefit, and maybe that’s a detriment. The unrealized potential of this story is likely greatly than the final product, but it’s still a worthwhile experience.

Eileen will be released in select theaters on December 1 before expanding to theaters nationwide on December 8.

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