Keira Knightley Goes Off the Deep End in ‘The Woman in Cabin 10’ Photos (Exclusive)

Keira Knightley is diving deep for her role in The Woman in Cabin 10.

The actress stars in the psychological thriller, based on Ruth Ware’s bestselling 2016 novel, as Laura “Lo” Blacklock, a travel journalist on assignment aboard a luxury yacht — where she witnesses someone being thrown overboard. But with all passengers accounted for, she is told it never happened.

Though nobody believes her account, Lo is determined to uncover the truth of what occurred that mysterious night, even if it means “putting her own life in danger,” teases a synopsis.

PEOPLE has exclusive new photos from the film, which director Simon Stone (The Dig) says finds its core characters, including Knightley’s lead, in a “kind of prison that you can’t get off of.”

“It’s a kind of trapped-in-a-bunker thriller, but it happens to be the most luxurious bunker in the world,” adds Stone, 40, of the setting on sea.

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The director says he wanted Knightley, 40, to approach the role of Lo differently from how female characters were often portrayed years ago, in the sense of them being “slightly unpredictable, and you don’t know whether they’re sane or not.” Meanwhile, thrillers from the ’70s through ’90s had a “very straight performance from an incredibly charismatic [male] lead,” like Kevin Costner, Richard Gere, Robert Redford or Warren Beatty.

“I was like, ‘No, I want this to feel like you are Kevin Costner,’ ” Stone says. “And she’s done an extraordinary job of having this incredibly charismatic core that you totally believe, because it’s a gaslighting story.”

“Historically, there’s this tendency of treating female psychology as something that’s not to be trusted. And I went, ‘No, I want the performance to be so convincing that you just go, “I believe you. I’m on your side, and I just want, with you, to find out what happened,’ ” he explains. “And [Keira]’s so good at that.”

The movie also stars Guy Pearce, Hannah Waddingham, David Ajala, Gugu Mbatha-Raw, Gitte Witt, Art Malik, Daniel Ings, David Morrissey, Christopher Rygh, Paul Kaye, Kaya Scodelario, Lisa Loven Kongsli, John Macmillan, Pippa Bennett-Warner and Ayọ̀ Owóyẹmi-Peters.

Stone says both Knightley and her character Lo are “no-bulls—” types of people. “Also, [Keira]’s incredibly smart and she plays with great intelligence in her acting. So there are totally overlaps,” he adds. “But, of course, Keira has aspects of all of the characters she’s ever played.”

In real life, Knightley comes from a performance background, as both her parents work in the industry — so that, plus her own experience, made her a pro in the role, regardless of its layers.

“She was pretty remarkable,” Stone says. “I was kind of astonished at how quickly she threw herself in the psychological situation. Because, of course, at the end of the day, we’ve ended up really hanging the whole film on the emotional rollercoaster ride [Lo] goes through.”

“[Keira] finds the nuance in every single moment, where we would joke a lot about, ‘How paranoid am I right now? Are we at level four? Are we level seven yet? How suspicious am I?’ ” he adds.

Filming The Woman in Cabin 10, in places like Scotland and Norway, certainly had its “tough” moments — primarily, that the 70-person crew had to be extra “respectful” about where they left their equipment while aboard an eight-cabin, $150 million yacht that meant very strategic shooting.

“It took a lot of convincing,” Stone says of being able to use the vessel at all. “We had different shoes for inside and different shoes for outside and we had to take our shoes off. It was all very crazy.”

At the same time, the cast “all got along really well with each other,” he says. “They had to, because when we left port on that yacht, we didn’t come back until 12 hours later.”

The actors also only had “two bedrooms” to “hang out in” aboard the yacht, as film-crew members and equipment occupied the remaining six rooms. And “there would be 15 of [the actors] all just hanging out” in those two rooms and “chatting away,” says Stone.

“They got really close and connected. It was great to have that unified experience,” he says. “In a studio or on a film set, you’ve often got these trailers that everyone can disappear to, and that’s a good thing because you need your own space. But the benefit in the other direction of these people being an ensemble was huge in terms of how easy and believable the performances are.”

How does The Woman in Cabin 10 stand out in the popular psychological-thriller genre? Stone points to “something fairly unprecedented that happens at the core of the movie that feels really epic, on both a psychological and a metaphoric level.”

“While there are elements that feel like they’re [within] the genre — and of course, that’s fun — the twist is pretty massive,” he says. “When you wrap your head around it and how we manage to pull it off as filmmakers, it is pretty satisfying.”

“The twist is similar [to how it unfolds in the book] but ‘How do you pull that off in a movie?’ is what I’m going to put out there,” Stone teases.

As for whether a follow-up film based on Ware’s recently released The Woman in Suite 11 will ever come to fruition, Stone says, “Let’s see how this film goes with the audience” first.

“If this is a property that people really dig, then of course there’s always interest in continuing it, I think, more than anything, continuing a character that Keira has invented so beautifully,” he notes.

“Obviously, Ruth invented the character [of Lo] in the book, but [Keira] kind of brought her to life in physical form, and I think people will love her,” Stone says.

The filmmaker adds of Knightley, “It’s hard to carry a movie if you’re in every single scene. In most films, the lead character has a bit of a break at some point, but [Keira] carries the whole film from beginning to end. It’s impressive.”

The Woman in Cabin 10 is on Netflix Oct. 10.