Like the lead character she portrays in the widely anticipated movie version of “Gone Girl,” Rosamund Pike fell off nearly everyone’s radar.

At the tender age of 21, the British actress was cast as the sultry Miranda Frost, a sword-wielding vixen in the James Bond film “Die Another Day,” her first studio feature. She powdered on enough makeup to look a decade older, donned a black sports bra, and met an untimely demise with a knife to her heart. Onscreen, she was killed by Halle Berry. Offscreen, she suffered a far worse blow to her budding career.

The baggage of playing a Bond Girl backfired. “It cemented a sort of patrician, frigid, English, standoffish cold image,” says Pike, over breakfast in September at the Toronto Film Festival. “People think I lie about my age. I never had a chance to do those young roles.” After her high-profile gig in the 2002 Bond picture, the actress persevered for years in supporting parts, in films such as “Pride & Prejudice,” “An Education” and “Barney’s Version.”

But all that changed in July 2013 when she landed her first lead in a movie — as Amy Dunne in David Fincher’s thriller “Gone Girl” — the most coveted role of the year. “I’ve always been given roles that are more mature than I am,” says Pike, 35. “Now it could be that it’ll all start reversing, and I’ll stay around 30.”

The film could reverse a career trajectory that until now had not been headed in the direction of stardom. There’s tremendous excitement building around her standout performance in the movie, which 20th Century Fox debuts nationwide Oct. 3. In “Gone Girl,” based on Gillian Flynn’s bestselling novel (8.5 million copies sold and counting), Pike stars as the perfect wife, who disappears from home one day, leaving police suspicious that her husband Nick (Ben Affleck) has murdered her. Amy is a riotous, multilayered role that every A-lister, from Reese Witherspoon to Olivia Wilde, chased after. But Fincher, who prefers to cast less-famous actresses (think Rooney Mara in “The Girl With the Dragon Tattoo”), hand-picked Pike to walk in Amy’s shoes.

Rosamund Pike 'Gone Girl'
Yu Tsai for Variety

The movie-star business could use a fresh force like Pike. The hot female superstars of the ’90s (Julia Roberts, Meg Ryan and Demi Moore) no longer headline blockbusters, and their replacements (Jennifer Lawrence and Shailene Woodley) are much younger. Other than Angelina Jolie, who is 39, there aren’t many actresses in their 30s who can carry a movie. “Amy has many sides to her, and Rosamund was able to really show one emotion to the next,” says Flynn, who also adapted the screenplay. “It’s a pretty thrilling and frightening talent.”

Fincher knew the challenge in casting Amy was that she’s hard to grasp. An important criterion for the director was that Amy feel like an only child, which Pike manages to convey easily, because she’s an only child of English opera singers. Fincher was familiar with the actress’ screen work. But it wasn’t until he sat down with her at the Four Seasons hotel in St. Louis, over a four-hour dinner that started with water and ended with whiskey, that he was convinced he’d found his Amy. “The role is really difficult, and Rosamund was born to play it,” Fincher says.

It was a terrifying prospect for Pike on many levels, all the more so because the actress fell ill with a 103-degree fever the night before production began in Missouri. “I threw up three times,” she says. “My body was going through a lot of changes.” It was the first time she ever had to report to a movie set on day one. “I’ve usually had the luxury of coming on a couple weeks into it,” she says. As she burned up, she fired off an email to an old friend — Tom Cruise. “I thought, ‘I’ve got to reach out to somebody who has been in this position,’ ” says Pike, who co-starred with Cruise in “Jack Reacher.” He promptly wrote back, telling her about his pre-fame jitters on 1981’s “Taps,” and offered a pep talk: “Trust yourself,” Cruise said. “You’re in the hands of a great director. You’re ready.”

SEE ALSO: Five Secrets from Gillian Flynn: ‘Gone Girl,’ ‘Utopia’ and More

Still, she wasn’t convinced. “There were frequent times when I’d just go home and say, ‘I’m going to give up,’ ” says Pike, who finally can breathe easy. When “Gone Girl” premiered at the New York Film Festival on Sept. 26, she was crowned the industry’s new “it” girl, with raves and talk of her first Oscar nomination (she attended the ceremony once, wearing a cardigan sweater over a borrowed dress). “The buzz about it is so daunting,” Pike says. “Obviously, because of Fincher and this book, the expectations are so fucking high. I rang up David, and said, ‘Come on, you’ve got to give me someone who doesn’t like it.’ ”

Pike packed her bags for Los Angeles last summer just four days after receiving her role-of-a-lifetime offer. She started to cry just as she left her London flat. It’s a memory she’s forgotten until her 2.5-hour interview with Variety. “I was unbelievably excited and unbelievably scared,” says Pike, who didn’t even get to tell her friends about the opportunity until she arrived at Heathrow Airport. “You suddenly feel so small. I thought, ‘I’m embarking on this thing I’ve always wanted.’ ” Her voice cracks. “I’m going to cry now,” she says, as her eyes well up. “Someone is giving me that chance, which is something I’ve wanted since I’ve been a tiny girl.”

Pike grew up in a middle-class London family. Her parents were college sweethearts, and she had a culturally rich upbringing, even if they weren’t financially rich. “I definitely found it hard to contain my feelings as a little girl,” she says. “Everything was big, and it still is.” She started to act at Oxford University, where she studied English literature. She paid for her tuition with TV jobs, including the BBC miniseries “Love in a Cold Climate,” directed by Tom Hooper. Pike is amused that people who meet her think she’s a posh, reserved Englishwoman. “I think I’m quite a wild person,” she says. “It’s fear of that which makes me come across as contained. Calm is something I’m fundamentally not.”

She’d often leave the “Gone Girl” set and play a game of ping-pong in the middle of the night or go for a swim. “Your adrenaline is surging, and it’s not making you rest,” Pike says. After Bond, she appeared in a sold-out West End play called “Hitchcock Blonde.” “I was naked onstage for 10 minutes,” she says. The London theater gave her the range that films didn’t, especially in a production of “Hedda Gabler.” “It allowed me a freedom of aggression,” she explains.

Rosamund Pike 'Gone Girl'
Yu Tsai for Variety

To prepare for the role of Amy, Pike enrolled in Fincher movie boot camp: 10 weeks of pre-production for the 106-day shoot that crisscrossed between Missouri and Los Angeles. As in all of the director’s pictures, actors were subjected to repeated takes. “He’s not doing it because he thinks you’re crap,” she says. “He’s giving you this gift, and allowing you to divest all your baggage.” She was proud of a bruise on her leg in one scene, but another bump incurred during a fight with Nick nearly gave her a concussion. “I think probably around take 18 of getting my head bashed against the wall, I literally saw stars,” she says. The first assistant director had to intervene.

Pike never toiled so hard. First, she had to channel Amy’s voice, an American upper-class, East Coast timbre reminiscent of Carolyn Bessette-Kennedy. She re-watched “Basic Instinct,” concentrating on Sharon Stone, and “To Die For,” where the Nicole Kidman anchor served as a prototype. Pike worked with a vocal coach four hours a day, reciting aloud chapters from Truman Capote’s “Answered Prayers” and high-society magazines. “We read from Town & Country and the New Yorker,” says Carla Meyer, the dialect coach who helped prep Cate Blanchett for “Blue Jasmine.” “We didn’t read down for Amy.”

Pike also had to dramatically transform her body. Because of the filming schedule, she had to gain and lose 13 pounds three times to play the character at different points in her life. “I was eating crap, eating well, eating crap, eating well,” she says. “Bulking up and leaning out.” She gorged on hamburgers and malts, and exercised with a professional boxer for up to four hours a day, running five miles (in 42 minutes), and lifting weights. During a shower scene, her onscreen husband complimented her svelte physique. “I know Mr. Affleck was a little envious of her abs,” says trainer Holly “Lil Bear” Lawson. “She looked amazing.”

“Gone Girl” was a much-talked-about title as soon as Flynn, a former TV critic for Entertainment Weekly, published the novel in June 2012. Just after its release, Universal began pursuing the rights, with Witherspoon interested in producing and playing Amy. But Fox managed to outsmart its rival when the studio’s then co-chief Tom Rothman, now chairman of Sony’s TriStar Prods., discovered that Universal had not closed its deal, and sprang into action. “ ‘Call the book agent and tell her you want to talk at 5 o’clock and insist that she has her client available,’ ” Rothman remembers telling his team. “ ‘Offer them $1 million, and tell them they have until 5:30.’ ” Fox landed “Gone Girl” by 5:20 p.m., and Rothman’s decisiveness paid off when the book turned into a literary phenomenon. (Witherspoon, who never owned the rights, boarded the project as a producer at Fox.)

Flynn took a pass at the first draft of the script, a condition of her contract. As she worked on the adaptation, Fox executives went straight to Fincher. “I only had one director in mind,” says the studio’s production president Emma Watts. Fincher read the book, but wasn’t sure how a movie would work — especially given the story’s split narratives. He skimmed through 60 pages of Flynn’s script, and became more intrigued. The two met for the first time in January 2013. “I spent a long time covering movies for Entertainment Weekly, and we all know how the story goes,” Flynn says. “If the author gets any say, they are pretty quickly fired. I was continually preparing myself for bad news.” But she and Fincher hit it off, and he started offering her notes. “I wish I had breathed and enjoyed the experience more,” Flynn says.

Fincher had an idea of who he wanted to play Nick, but the project would rest on the casting of Amy. In the summer of 2013, Pike was in Glasgow on a six-week shoot of an indie film called “What We Did on Our Holiday” when she got word that Fincher wanted to meet over Skype. “And then it was interesting, because the agents get cut out in David’s process,” Pike says. “You get this really protected line of communication. It became me and either his assistant or his wife who would be dealing with the communication.” Pike had three lengthy Skype talks with the director, and she read the book between their meetings. “It’s your perfect book club really,” she says. But there was also the pressure of showing him that she understood Amy, without actively auditioning. “It was a bit like being X-rayed,” she explains. “You feel like you’re being scanned. You’re having a conversation, but you realized you’re being observed.”

It was during those Skype conversations that she realized she was in the running: “I can see you know that I have this character in me,” she told Fincher. He wanted to meet in person, so Pike took an overnight flight from Scotland to St. Louis. As she was about to take off, she received an email (subject line: “David Fincher: For Your Eyes Only”) with the script. She read it twice on her iPad. “We talked about the transformation,” she says. “He wanted to see where my vanity lay, and whether I would be prepared to go to some places.”

Pike learned on the last day of shooting “What We Did on Our Holiday” in a remote area of Scotland that she had gotten the part. “It always happens with the most critically important events in my life, I’m always somewhere with no cell phone reception,” she says. “One text managed to filter through from my manager, saying, ‘We’re getting the offer.’ ”

It wasn’t just sweat and tears that went into playing Amy. There was also a lot of blood. “I think if David hadn’t been worried about animal rights, he would have used pig’s blood,” Pike says. “It is one of the hardest things to get screen blood to have texture and get it to dry in the correct way. Blood goes through so many stages as it dries. It becomes sticky and changes color. And arterial blood is different from other types of blood. We had many blood tests.” She had to wash herself constantly. “I had so many showers” — up to 20 a day, she estimates — “Your skin becomes raw.”

“Gone Girl” is rated R, and Pike is delighted that the MPAA cites the film for nudity as well as for violence, sexual content and language. She reveals that all the nude scenes were shot without body doubles. The most complex sequence is a graphic love scene with her obsessive ex-boyfriend Desi (Neil Patrick Harris). To rehearse, the two actors stripped to their underwear in a private soundstage and practiced mock-sex for hours. “As an actor,” Pike says, “you’re happy to take your clothes off in front of lots of people, but if it’s just you and another actor, it’s weird.” She collaborated with Fincher and Affleck to rewrite some of the scenes in the film’s finale, and suggested the oral sex act that Nick performs on Amy early in the film. “That’s a side of Rosamund Pike that people don’t expect,” she says with a grin.

Even if her big, starring role is quite melodramatic, Pike has a comedic side too. Over breakfast, she talks about how much she loves “Bridesmaids,” and sometimes sounds like a Nora Ephron character. “Are you going for the waffles?” she asks, before deciding not to order smoked salmon because it doesn’t go with French toast.

Pike hopes the role of Amy will give other filmmakers a sense of her range as an actress. “I want to be stretched,” she says. “I want people to know I’ve got a big wheelhouse, and I want them to explore it. It’s about directors, I’ve realized too late on. You can be a great actor, but you’re not going to get anywhere without a great director.” She says that after she saw a rough cut of “Gone Girl,” she wasn’t impressed — by her own performance. “I thought Ben was absolutely astonishing, and I thought I was sort of lacking,” she concedes.

Pike is still in that strange place before she’s about to get bombarded by fame. She asks if she looks the same in real life as she does on the bigscreen (she does), and she’s not sure how she feels about losing her anonymity. When she’s not working, she lives in London with her partner, Robie Uniacke, and their 2-year-old son Solo. Even though she’s had myriad offers, she’s taking a hiatus for now.

But it’s not a calculated decision. Pike is pregnant with her second child. “I haven’t been available,” the actress says. “It’s a very surreal thing that people in Hollywood are now discussing my due date.” She looks down at her stomach. “He’s kicking right now, telling me, ‘Come on, Mom!’ ” And after that delivery, Rosamund Pike will be ready to give birth to her new career.