“Sometimes I think, ‘What will happen if everyone forgets about me?’ ” Gwyneth Paltrow says over iced tea on a sweltering day in Tribeca. “What happens if, one day, I say, ‘OK, I’m ready to go back to work,’ and people are like, ‘So? We don’t care. We don’t want you.’ ”

Although she’s been less in the limelight lately while tending to her 16-month-old daughter, Apple, and spending time with her husband, Coldplay frontman Chris Martin, Paltrow’s concerns seem a little premature and more than a bit unlikely. After all, this is an actress who occupies an interesting niche in the business: Her reputation and A-list profile are seemingly untouchable, despite her films’ inconsistent box office.

Yet Paltrow appears to be in the throes of a career crisis. For every comment she offers about the rewarding, artistically energizing experience of playing Catherine in Miramax’s upcoming film adaptation of David Auburn’s play “Proof,” there’s another along the lines of “I could definitely never do another movie,” or “I’m just not going to leave (Apple) to do something I’m not totally, like, obsessed with,” and even “Sometimes I think, well, maybe I just want to have tons of babies. You know?”

Plus, in this Apple-centric era Paltrow says box-office number-crunching means “absolutely nothing” to her. She’s just not interested in “putting money in someone’s pocket.” Part of this is being able to sleep well at night by just making family-oriented decisions (she says she used to lie awake worrying), so pursuing the kinds of roles that she can be “obsessed with” depends on an ability to tune out the bottom line.

Paltrow is honest about her film choices (including some stinkers like Miramax’s “View From the Top”) and savvy about the box-office draw she does have. She points out that most of the films she’s done that were supposed to make big bucks — “Shallow Hal” and “A Perfect Murder,” for example — were successful (both these films took in about $70 million domestically). “Not the $200-million–scale successful, but enough,” she says. “If you do a movie that’s supposed to be huge and it’s not huge, that’s where you get hurt. I haven’t done that, so maybe that’s why I haven’t been shut out.”

Meanwhile, the films Paltrow has cared about and believed in — among them “The Royal Tenenbaums,” “The Talented Mr. Ripley” and “Shakespeare in Love” — have turned out relatively well, both at the box office ($52 million, $81 million and $100 million, respectively) and come awards season. (“Shakespeare” won her the best-actress Oscar in 1999).

Yet for now, as she deliberates her next move, Paltrow wants the world to know that things have changed. From now on, the movie star will be taking a backseat to the mom. Whether Hollywood’s powers that be choose to accommodate her new schedule is, frankly, their problem. For now.

Paltrow was on a flight to New York with her friend Jennifer Jason Leigh when she first heard about the role of Catherine. Leigh had just bucked her agents’ advice not to sign on for a heavy theater project and was en route to take over for Mary-Louise Parker in the role on Broadway. “She kept saying, ‘But it’s such a good part. It’s such a good part!’ ” Paltrow says. “I just remember thinking, ‘Isn’t that fantastic?’ Something really challenging, really fulfilling. And that feeling stayed with me.”

At the time, despite having just done “Sylvia,” Focus Features’ dark, haunting biopic of writer Sylvia Plath — one of her lifelong dreams — Paltrow was having a hard time finding challenging roles. She may be reluctant to go through the full list, but she’s unambiguous about her feelings regarding such ill-chosen vehicles as “View From the Top.” (“That was just bizarre,” she says. “They chopped it into a totally different film, a film I wouldn’t have done if I had gotten that script.”)

“There was a certain point where, like, I really took stock of everything,” she says. “I thought, ‘Why did I get talked into that?’ ‘Why did I get talked out of something that was brilliant, that I really wanted to do?’ ‘Why have I made some choices that I’m not proud of?’ ” Somewhere in the midst of this, she says she lost her love for acting. “I just would think, ‘Why am I doing this?’ ” she says.

When “Proof” director John Madden, who had guided her Oscar-winning performance in “Shakespeare in Love,” approached her with the idea of playing Catherine at the Donmar Warehouse in London, it was just what she needed.

Like any Hollywood A-lister who steps onto the boards, Paltrow’s turn as Catherine was intensely scrutinized. But doubters were surprised. The Guardian’s Michael Billington wrote: “So, how good is Gwyneth Paltrow? On the evidence of her performance in David Auburn’s award-winning ‘Proof,’ I would say she has definitely got the theatrical gift: Watching her, one can easily imagine her in a long line of Ibsen and Chekhov roles. … she makes Auburn’s play look substantially better than it is.”

The film is likely to earn her an equally warm reception. In it, twentysometing Catherine has put her life and her college education on hold to care for her father (played by Anthony Hopkins), who is one of the world’s most gifted mathematicians but whose mind is slowly deteriorating. Catherine may have inherited her father’s brilliance but is terrified that her gift also comes with the burden of mental illness. In the role, Paltrow manages to boil all of the tormented, self-conscious body language she was praised for on the stage down to intensely felt subtleties: the remote, emotionally disconnected glance, the vulnerable, doubting tilt of the head, the wild, gaping eyes. The task of conveying every nuance, twist and turn of the plot falls almost solely to Paltrow; she centers the film.

For Madden, this is a specific Paltrow knack for “getting under the skin of what she’s doing,” he says. After three intense collaborations, he is well versed in the actress’ gestures and ticks; according to him, Paltrow immerses every part of her body — from her eyes and facial movements to the palpable rhythm of her breath — into a role. “It isn’t calculated,” he says. “I think it’s the engagement of head and heart.” But, despite the fact that he can describe every habitual flutter of her long, articulate fingers, Madden says he only really knows Paltrow professionally — which is exactly what made her perfect for Catherine. “It would embarrass her to hear it,” he says, “but I think Gwyneth really knows this character because she has this sense of being slightly special, slightly isolated. There’s an apartness to her. She’s incredibly gregarious but also intensely private. It makes her able to understand the hermetic world that Catherine inhabits.”

One of the things that most impressed “Proof” co-star Anthony Hopkins was Paltrow’s ability to get the job done despite the emotional tidal wave that had recently crashed through her life.

“When I watched the rough cut of the film, it crossed my mind that it must have been quite painful for her to do that role at that particular time,” he says, referring to the then-recent (2002) death of Paltrow’s own father, TV director Bruce Paltrow, with whom she had been profoundly close. “But I found her very uncomplicated. She arrived on the set on time, she did her job. She’s very practical about the acting business. I like that.”

In fact, that disciplined behavior had everything to do with her father — Paltrow says that the professionalism, courtesy and obsessive punctuality for which she is known all come from her parents.

“My father died in between doing the play and doing the film,” she says. “When I was doing the play, I was relating to the fear that my father might die, when he was going through everything, as opposed to the knowledge that he did die. I don’t know how to articulate it, but understanding death and fearing it are two different things. You go through an experience like that, and then you’re suddenly playing a character that is totally defined by her father’s death. I have the same thing. So it’s very … it’s uncanny.”

She had also just married Martin and was secretly pregnant with Apple through part of filming, both events that Madden considers transformative. “If you want to see the real Gwyneth, you have to see her around her family,” he says. “Emotionally, she is a person who has landed.”

It also brings out a side of Paltrow that’s not so sugarcoated: the mother lion. She and Martin have made a heroic attempt to reclaim their private lives, including having a top-secret, no-guests wedding and famously cheating the paparazzi out of a photo of them leaving her gynecologist’s office two years ago by having their own photographer snap the picture. Their recent move to Tribeca is the latest step in the strategy. In her old neighborhood, the celebrity-crowded West Village, “It was not OK.” Photographers, camped out right on her corner, were guaranteed a shot of any number of area residents. The new digs, she’s hoping, will be a little further under the radar.

Meanwhile, in London, where the couple spend more than half their time, she’s become her own paparazzi security force. “If I have my daughter in the car and they are making me nervous, I’ll do whatever I have to do,” she says, matter-of-factly. “I keep a whole log. I take pictures of their cars, write down license plate numbers, everything. If they do it again, I can go to the police. I know my rights, and believe me, I will have them arrested. I’ll stop at nothing.”

Equally fierce is her determination to chart her career around her family’s needs. “Proof” was filmed pre-Apple; since her birth, the only role Paltrow has shot has been a small part in another dark tale of mental illness, Sony’s “Running With Scissors,” based on Augusten Burroughs’ memoir, directed by Ryan Murphy and starring Annette Bening. Paltrow plays Hope, the eldest daughter of Burroughs’ psychiatrist, whom she describes as “a totally insane old maid.” She also recently directed her first short film with friend Mary Wigmore as part of an upcoming Glamour magazine “reel moments” series (with Apple always nearby on the New York set, of course).

Paltrow waves off rumors that she is interested in starring in and producing a biopic on Marlene Dietrich: “Yes, but that’s just in development. We haven’t decided anything yet.” At the suggestion that producing a film would be a pretty intense workload, she says lightly, “I know. Maybe I’ll just hire another actress.”

As for other projects, they’ve all been turned down because “scheduling-wise, they just haven’t worked out for my family.”

For Paltrow, there has been no better role model of personal and professional balance than her own mother, Blythe Danner, whose resume has been busier than usual the last couple of years. This year, Danner, whose career was on the backburner for most of her two kids’ childhoods, was nominated for three Emmys for her roles in “Will & Grace,” “Huff” and the TV movie “Back When We Were Grownups.”

“When I heard that, I almost burst into tears,” says Paltrow. “Here’s a woman who gave up so much to be with us and my father. And I just think it’s so great that she’s finally getting the recognition she deserves.”

Yet as far as Madden is concerned, the idea that Paltrow would follow in her mother’s footsteps and not do another film anytime soon is unlikely. “Of course she will. But it isn’t the same voracious need,” he says. “It doesn’t define her anymore.”

Paltrow admits that, “The artist in me, for lack of a better word, is definitely brewing,” and that, ideally, she would like to do one play or one film, per year. So long as it doesn’t interfere with the family. –JULIA ELLIS

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