The mother of all thrillers

"When I did my mohawk for the third movie he was with me when I shaved my head. And he was with me when I pierced myself. I wanted him to see me transform into her."

Wasn't she worried he would one day ask for a similar haircut? "You know what," she laughs down the line from Berlin where she is filming, "he actually has a mohawk today." Certainly beats a Mother's Day card for an expression of admiration.

Rapace's son has become used to mummy's hair-changing, shape-shifting ways. After playing Salander, the computer hacking punkette, the Swedish actress went on to become a tousled haired traveller in Sherlock Holmes: A Game of Shadows. In the summer she will be seen as a space explorer in Ridley Scott's Prometheus.

Babycall is one of her most dramatic transformations yet. A psychological thriller about a single mother, Anna, who has fled an abusive relationship, it's a role that asked a lot of Rapace. "I became a little bit obsessed with it," she acknowledges.

First to go was her usual exercise routine. Anna, beaten down by life, is the antithesis of the lioness-like Salander. Come the second week of the four-month shoot, Rapace, 32, woke up with an ache in her hips. "I had pain for the rest of the shoot. I went to doctors, specialists and no-one could understand what it was. When I was finished it disappeared the next day."

She was on her own in Oslo to make the movie while her son stayed at home with his father, the actor Ola Rapace, in Stockholm. When she went home at weekends she found Anna's troubles shadowing her. "My husband said to me, 'Noomi, how far are you going to go? I don't know if this is good because you're not yourself when you're coming home ...' I couldn't understand what he was talking about. It's hard. I never really reflect or analyse myself when I'm inside the part, inside the process of making the movie. It's when I'm done with it and can look back, I can see how deeply affected I was, and I was not really myself."

When we speak she has just come back from a night shoot. There are a couple of hours before another hair appointment – this one to make her lighter – then it's back on set at 4pm to work through till 2am. A nap is probably not on the agenda. "I'm not good with sleeping," she laughs.

Just as well. Since she signed up for the first Millennium movie, it has been pedal to the metal for Rapace's career. Being Stieg Larsson's heroine ate up a year and a half. A long time to walk around in anyone's biker boots. Rapace, the daughter of an actress and a flamenco singer, says she doesn't miss Lisbeth. "In the end I was so exhausted and almost quite close to the edge. It was good to let her go."

Despite the success she has had since, Rapace was treated at one time like the Jennifer Aniston of the kick-ass heroine world. Just as some magazines like to commiserate with Aniston, a multimillionaire actress and producer, for her "tragic" lack of a husband, so Rapace was besieged with inquiries about how upset she must have been when the Hollywood remake went ahead with David Fincher directing and Rooney Mara as Salander.

Her answer to such inquiries is that she wasn't upset. Been there, done that, had the mohawk. "I was relieved to have another actress stepping into her. I did my version, I gave her my spirit, and now it was up to someone else." She still hasn't seen the American version yet. "I really respect David Fincher, I think he's a great filmmaker, so I will see it. I've just been crazy busy with other things."

Those "other things" include sparring verbally with Robert Downey Jr and Jude Law, playing Holmes and Watson, in Guy Ritchie's 2011 film. The movie might have been a Brit comedy caper, but as her first English language film, Game of Shadows was a serious business for Rapace. She only started to learn English three years ago. "I decided to learn when I had my first press conference for The Girl With the Dragon Tattoo. It was such a nightmare, so horrible, I was sitting in front of all those journalists and I couldn't express myself, I couldn't talk to them. I was so embarrassed and angry."

She started to study on her own, reading books and watching TV and movies without the subtitles. Again, she found herself lost in the task at hand. "I forgot it was not my language. When I did Prometheus I was dreaming in English and texting my mum in English."

Ah, Prometheus. Judging by the internet chatter, it's the stuff of a zillion science fiction fans' dreams. In a cast that includes Michael Fassbender, Charlize Theron and Idris Elba, Rapace plays Elizabeth Shaw, one of a team venturing into deep space.

"It was a big movie to step into, really physical and some scenes are quite disturbed and hard on you. But I always left the studio smiling. I don't know what he [Scott] does but he's just incredible to work with."

There was one member of the cast with whom she really clicked – Scot Kate Dickie. "I so much want to work with her again. I was just texting her a couple of days ago saying, I want to find something to do with you. She's brilliant, I was blown away by her."

Whether audiences will be blown away by the big budget Prometheus in June is the question. "It's always hard to live up to expectations. I remember when I stepped into Lisbeth I felt like this was a suicide mission because everybody sees Lisbeth in a very personal way in their heads, everybody had read the books, and now I was the one bringing her to life."

All she will say of Prometheus is: "It doesn't look like anything I've ever seen. It's going to be something else."

When she has finished filming the Brian De Palma-directed thriller, Passion, in Berlin, her to do list includes Knockout, the story of the Swedish boxer Bo Hogberg. Playing Hogberg is Rapace's now ex-husband. They remain friends. "We're a good team."

A move to Los Angeles isn't for her. London is calling instead. "I want to stay in Europe. I feel very European and I love European films. They're very brave." She's an admirer of Andrea Arnold (Wuthering Heights, Red Road) and Steve McQueen (Hunger, Shame). Her ambition is to do both, the big movies and the smaller indies.

"I want to mix it," she says. Between Salander and mohawks, she already has.

Babycall is out in cinemas on March 30.