I, on the other hand, get a crackling line and a revelation. She's not in Detroit at all, it turns out. She's a couple of kilometres up the road. And she still won't meet me.
"Oh God," she says, when I finally get her. "I'm so sorry."
I didn't know you were going to be in Britain, I say. "I didn't know I was going to be here either. It just happened. I've just come to see family and then I'm leaving. I'm so sorry." It's hard to know what's going on. "I always do my interviews face-to-face," Weisz says. She does, it's true. Or at least she did. But then her circumstances have changed rather dramatically in recent months.
Last November, she and her partner, film director Darren Aronofsky, with whom she has a 5-year-old son, Henry Chance, announced that they were separating. A month later it was revealed she was dating Daniel Craig - they had worked together on a film, Dream House, last year - and he'd subsequently split from his long-term fiancee, Satsuki Mitchell.
And then, in June, it transpired Weisz and Craig got married in a low-key ceremony in New York with just her son, his teenage daughter and two family friends present.
There have been rumours on the internet that she's pregnant - could that be why she doesn't want to meet in person? Or could it be the influence of the notoriously tight-lipped Craig, who refuses to ever talk about his personal life? The only pictures of them together are of him looking faintly murderous toward the photographer.
Or is it, simply, like she says, some sort of bizarre misunderstanding? Who knows? Though I do wonder if suddenly becoming one half of an extremely famous couple has changed things. Is she feeling a bit hunted?
"No I really don't, actually. Maybe I'm just not interesting enough. But no, I haven't felt hunted at all."
"But you've made a decision as a couple not to talk to the press?"
"I think that both of us ... yes," she says simply and waits for the next question. In fact, it's another condition of the interview that I won't ask her about Craig. Anyway, it'd be pretty hard for her to, given the circumstances. He told a magazine that talking about her would be "like shooting [her] in the back".
Henry, on the other hand, her son, sitting in the back seat of his car with his nanny, is desperate to insert himself into the interview. At one point when Weisz is talking about the lack of female directors in Hollywood, a small voice pipes up: "What's female?"
"Female is a girl, darling," says Weisz. And then, "Yes, that's right. It means there's enough boys." (I do wonder how this might be relayed back to Daddy, a boy director.) Still, it's a vivid illustration of what's involved in being a working mother. "It is hard. But then for every single working mother in the world it's complicated and difficult. I feel like I'm one of the many working mothers. And I only have one child. I know working mums who have three or four. It's definitely a challenge but it's a wonderful challenge to be able to do both."
Weisz was brought up in leafy Hampstead Garden, north London, by her Viennese mother and her father, a Hungarian inventor, and I wonder if the fact that her mother was a psychotherapist has made her think about the way she's bringing up her own child.
"I don't think so, no. For me, being a mum has been a really, really instinctive thing."
As is acting. She's not sure, she says, where the drive to perform sprang from. "I wasn't at all the star of the school play. I wasn't getting up on tables and singing. It was more of a secret, really. I don't know. For me it's all about disappearing. When people think of performing they usually think of show-offs, but I think of it more that you disappear into somebody else."
In fact her teenage years were fairly troubled, though she's reluctant to talk about it. Her parents divorced. She went through three expensive private girls' schools. It's usually said that she was expelled from the first two, but the last time the Observer printed that, her mother wrote in to say it wasn't true.
She had "a problem with authority", says Weisz.
Her mother had wanted to be an actress herself in her youth: she was the one who queued for tickets for King Lear on behalf of her daughter in 1986, and seeing it "was one of the reasons I was inspired to act", says Weisz.
Seeing, that is, one actor, in particular: Bill Nighy. "It was just one of the best performances I've seen. It was just like Mick Jagger came on stage or something. It was pretty extraordinary."
And two and a half decades on, she's finally getting the chance to act with him in an MI5 thriller.
"I was a fan. A proper fan. I'd go and see him in things and then go backstage and knock on the door and he's always said to me that I liked him before anyone else. And we've always said, 'let's find something to do together'.
"And we would text each other now and again to say, 'have you found anything?' And we hadn't. Until David [Hare] offered us Page Eight. So it's been a really long time coming. A couple of decades."
The result is a spy thriller of the sort that simply doesn't get made any more. Or at least, not as this one is, for television. Nighy is Johnny Worricker, an old-school MI5 agent - decent, uncorrupted, increasingly cast adrift - who's being forced to deal with the realities of the post-Iraq world. It's a big subject - the post-Blairite realpolitik of how a government deals with its own intelligence agencies. And it has a truly stellar cast. As well as Nighy and Weisz, Michael Gambon plays the head of the section and Ralph Fiennes is the Prime Minister.
Weisz is as magnetic on screen as she always is. It's hard to take your eyes off her, as she inhabits the kind of character that in recent years she's made her own: a woman of passion and commitment. The Observer, however, noted, that "the 20-year age gap between Nighy and Weisz is the kind of thing that could draw ridicule".
Weisz bristles when I mention this. "I'm not sure how old Bill is. Do you know? I'm 41. You need to google it. We're not making out. There's one very delicate kiss in the last frame of the film, which is incredibly tender.
"They connect with their hearts and they have a great amount of empathy. Anyway, I think people of all sorts of different ages can get it on. It doesn't bother me."
Is it my imagination? Or simply a crackly phone line? Weisz seems to alternate between full-force charm and a certain belligerent defensiveness.
She keeps telling me how great my questions are. And then refuses to answer them.
I try to talk to her about ageing, but turning 40, she says, was "so not such a major milestone". And the pressure to look good? "I think as an actor, you have to look after yourself," she says. "It's like being an athlete. You have to look after yourself and work out."
But you haven't felt like you might have to have things lifted or tucked at some point?
"Oh God. Ask me in a few years. I feel a bit too young for that. Maybe I'm deluded. I don't have a philosophical problem with people who do things like that. It's really up to them. But personally, I'll just have to see how I go."
Pretty well, so far; and there's no shortage of roles. After the Oz film, she starts filming on the new Bourne vehicle, starring alongside Matt Damon.
Are there any family tensions? With her husband doing James Bond, does it feel disloyal to be doing the other great spy franchise? I wonder.
"No. There's no tension. I guess there's a B, an O and an N but they're very different. Bourne is American and I'll be playing American. It's Americana. And Bond is very, very English. I think it's culturally, tonally, very different."
Logistically, though, it's obviously not the easiest thing being two actors in a new relationship, with a young child. Henry will go with her and the nanny to Detroit to film Oz, she says, but he starts school in a few weeks.
"And I think it will affect things." she says. "It'll be up to him a bit. He might not want to come ... So far he comes with a nanny and hangs out on set."
In past interviews, Weisz has said that acting is all about choices: making the right choices.
"Well, yes," she says. "Like life. You just never know at the time how things are going to turn out." And she's still, she says, "fiercely" ambitious. But having a school-age child will inevitably affect her choices now. "There are certain things that are now out of the question. Absolutely."
It must be tempting, I say, if you're married to another actor, to do a film together simply so that you can be in the same place for a bit.
"We've already done one. Maybe one day. It's not something we've been thinking about right now. We've been offered some plays."
Is that something you want to do? More theatre?
"Yeah. I'd really love to do a play next year."
Given she won an Olivier award last year for best actress for her role in A Streetcar Named Desire at London's Donmar, she'll surely get her pick of the parts.
But then things do seem to have a habit of coming her way, although she's astute enough to acknowledge this.
At 15, she won a part in a major Hollywood movie, King David, playing opposite Richard Gere, but her father put his foot down and wouldn't let her take it. It wasn't a truly terrible blow, she says, because "I wasn't burning to act. It was something which came later on. It just came my way."
And it would come her way again, after studying at Cambridge. And when I ask her about the struggles of her 20s - she's said in the past that she had problems getting out of bed some days and underwent a long stint of therapy - she says, "I think moaning about what a hard time I had in my 20s would be pretty bad taste. I've had a very privileged life, wouldn't you say? Looking at it from the outside? It looks pretty good, doesn't it?"
It does. Although, when I listen to the tape later, I can't quite catch the tone of this. She has, admittedly, recently shacked up with James Bond, but any woman who's just come out of a nine-year relationship and divorced the father of her child hasn't had it all roses, has she?
Is she being ironic? Or just super-literal? I'm really not sure.
But I suspect that looking at Rachel Weisz from the outside is now probably the closest anybody is going to get.
- OBSERVER
