Anne Hathaway breaks down the sinister motivation behind Rebecca and Eileen's kiss in 'Eileen'

• Anne Hathaway and Thomasin McKenzie star in the new drama "Eileen," based on the best-selling novel.
• The two stars spoke to Business Insider about the complicated emotions behind their onscreen kiss.

Set in 1960s New England during a few bitterly cold days leading up to Christmas, the new thriller "Eileen" explores the dangerous infatuation between the title character (played by Thomasin McKenzie), a dowdy secretary at a boys prison, and Rebecca Saint John (Anne Hathaway), the glamorous and unapologetically feminine new counselor who immediately turns heads when she joins the prison staff.

Eileen quickly becomes obsessed with Rebecca after a drunken night out: as the two are heading home, Rebecca remarks that Eileen has a face "like a Dutch painting," and says she probably has "fascinating dreams." The two women share a kiss before departing into the cold night.

But this is no love story. Instead, "Eileen" is a sinister tale of revenge, sexual abuse, and murder, complete with a seriously bonkers twist. Throughout it all, Eileen and Rebecca remain inextricably linked, though the reasons they're drawn to one another are a bit more complicated.

For Hathaway, the key to understanding the motivations of her mysterious character Rebecca lies in how she weaponizes her femininity.

"I just thought of Rebecca as being someone who… had sort of made a deal with the devil," Hathaway told Business Insider. "She knew that she, being a woman entering a world that had been largely defined by men — she's just going to get hit on, and she decided to turn herself into someone who it would be fun to hit on and she can handle it."

According to Hathaway, there is a lot more at play during Rebecca and Eileen's kiss than just attraction. She said she didn't necessarily think of Rebecca as being explicitly attracted to women.

"I think that she's someone who enjoys power, and I think that she's someone who enjoys the act of seducing without really thinking about the consequences," Hathaway said, adding that Rebecca's perfectly manicured exterior serves as her protection from the outside world.

McKenzie shared a similar sentiment about her character Eileen's sexuality, noting that Eileen has sexual fantasies about her male coworker in addition to her intense connection with Rebecca.

"I don't think she really acknowledges herself or is aware of, 'Do I like men, do I like women?'" McKenzie told Business Insider. "She feels so much desire that hasn't been able to be released in any way. And so the moment someone presents an opportunity for connection and for intimacy, she will latch on."

Despite all of this contemplation on their characters' motivations, sexual or otherwise, both Hathaway and McKenzie said that filming their kiss was essentially just another day at work.

"I think that when you're doing it, you don't really put a premium on it," Hathaway said of filming kissing scenes. "I get what from the outside, you think that it would, but when you're on set… I don't mean to play down or minimize it, but kissing someone is the exact same acting challenge as talking to them or dancing with them or doing anything."

"Dancing may be even more stressful for me," McKenzie joked.

"They were all liquor warm and it had been a good night. It had been a stressful day and there was a bit of release," Hathaway added. "So it just felt like the thing to do."

"Eileen" hits theaters December 1. Watch the trailer below.