"I've been police-checked," Nikki says suddenly. "Another medium called the police on me. I've been accused of emotionally damaging the children."

"And what did the police do when they came?" I ask.

"They laughed," Nikki says. Then she pauses and adds: "They told me they wanted to bring their own children here."

Maybe they were just saying that to be polite. Or maybe they meant it.

A Message from G.o.d

It's a Wednesday evening in early summer, and you'd think some high-society soiree was taking place in Knightsbridge, West London, on beautiful lawns set back from the Brompton Road. Porsches and Aston Martins are parked up and down the street, and attractive young people, some famous, in casual wear and summer dresses are wandering up a tree-lined drive. But this is no soiree.

We are agnostics. We are entering a church-the Holy Trinity Brompton (HTB)-to sign up for the Alpha Course, led by Nicky Gumbel. He is over there, welcoming agnostics; he's good-looking, tall and slim. It sounds impossible, but apparently Gumbel's course, consisting of ten Wednesday evenings, routinely transforms hardened unbelievers, the entrenched faithless, into confirmed Christians. There will be after-dinner talks from Gumbel, and then we will split into small groups to discuss the meaning of life, etc. There will be a weekend away in Kidderminster. And that's it. Salvation will occur within these parameters. I cannot imagine how it can work.

But many thousands of agnostics have found G.o.d through Nicky Gumbel. To name one: Jonathan Aitken, the former Conservative cabinet minister imprisoned for seven months in 1999 for perjury against the Guardian newspaper. "I am a man of unclean lips," he told the Catholic newspaper the Tablet, "but I went on an Alpha Course at Holy Trinity Brompton, and found great inspiration from its fellowship and the teachings on the Holy Spirit." The Tablet added, "He has done Alpha not once but three times, graduating from a humble student to a helper who pours coffee."

Nicky Gumbel's supporters say that within Church of England circles he is now more influential than the Archbishop of Canterbury; they claim that Gumbel is saving the Church. Other people say some quite horrifying things about him. I was told it is almost impossible to get an interview with him. His diary was full for three years. His people were apologetic. They said that the only way to really get to know Nicky, to understand how he does it, was to enroll in Alpha.

"Hi!" says a woman wearing a name tag. "You're ... ?"

"Jon Ronson."

"Jon. Let's see. Great!" She ticks off my name and laughs. "I know it feels strange on the first night, but don't be nervous-in a couple of weeks' time, this'll feel like home."

I drift into the church. There are agnostics everywhere, eating shepherd's pie from paper plates on their laps. Michael Alison, onetime parliamentary private secretary to Mrs. Thatcher, is here. So is an exEngland cricket captain. I spot the manager of a big British pop group. The famous former topless model Samantha Fox found G.o.d through Nicky Gumbel, as did Geri Halliwell. I wonder whether Jonathan Aitken will pour the coffee, but I can't see him. And now Nicky Gumbel is onstage, leaning against the podium, smiling hesitantly. He reminds me of Tony Blair.

"A very warm welcome to you all. Now some of you may be thinking, 'Help! What have I got myself into?'" A laugh. "Don't worry," he says. "We're not going to pressurize you into doing anything. Perhaps some of you are sitting there sneering. If you are, please don't think that I'm looking down at you. I spent half my life as an atheist. I used to go to talks like this and I would sneer."

Nicky is being disingenuous. We know there are no talks like this-Alpha is uniquely successful, and branching out abroad, so far to 112 countries, where they play Nicky's videos and the pastor acts the part of Nicky. "This just may be the wrong time for you," says Nicky to the sneerers. "If you don't want to come along next week, that's fine. n.o.body will phone you up! I'd like you to meet Pippa, my wife."

We applaud. "Hi!" says Pippa. "We've got three children. Henry is twenty, there's Jonathan, and Rebecca is fifteen."

Nicky a.s.sures us that we are not abnormal for being here. The Bible is the world's most popular book, he says. This is normal. "Forget the modern British novelists and the TV tie-ins," he says. "Forty-four million Bibles are sold each year." He says the New Testament was written when they say it was. "We know this very accurately," he explains, "through a science called textual criticism." He says Jesus existed. This is historically verifiable. He quotes the Jewish historian Josephus, born AD 37: "Jesus, a wise man, if it be lawful to call him a man, for he was a doer of wonderful works ... the tribe of Christians so named after him are not extinct to this day." I am with Nicky so far. But the agnostics here-it soon becomes clear that Nicky can read our minds-are thinking, "But none of this proves that Jesus was anything more than a human teacher."

Nicky tells an anecdote: He says that he once failed to recognize that his squash partner was Paul Ackford, the England rugby union international. Similarly, Jesus's disciples, in the region of Caesarea Philippi, failed to recognize that their master was the Son of G.o.d.

I could live without the squash anecdote.

Nicky says that Jesus could not have been just a great human teacher. When he was asked at his trial whether he was "the Christ, the Son of the Living G.o.d, he replied: 'I am.'" Nicky's point is this: A great human teacher would not claim to be the Son of G.o.d.

"You must make your choice-either this man was, and is, the Son of G.o.d, or else he's a lunatic or, worse, the Devil of h.e.l.l. But don't let us come up with any patronizing nonsense about his being a great moral teacher. He hasn't left that open to us. He didn't intend to."

This final logic (a quote from one of Nicky's heroes, C. S. Lewis) is impressive to me. It remains in my mind.

Then it's on to the small groups. I am in Nicky's group: As is typical, it consists of around ten agnostics, some from the City, one a professional sports person, strangers gathered together in a small room in the bas.e.m.e.nt. We sit in a circle. I wonder what will happen to us in the weeks ahead. For now, we gang up on Nicky and his helpers: his wife, Pippa, an investment banker called James, and his doctor wife, Julia, all ex-agnostics who found Christ on Alpha. We ask them antagonistic questions. "If there's a G.o.d, why is there so much suffering?" And: "What about those people who have never heard of Jesus? Are you saying that all other religions are d.a.m.ned?"

Nicky just smiles and says, "What do the other people here think?"

At the end of the night, Nicky hands out some pamphlets he's written called (such is the predictability of agnostics) Why Does G.o.d Allow Suffering? (answer: n.o.body really knows) and What About Other Religions? (answer: They will, unfortunately, be denied entrance to the Kingdom of Heaven. This includes me-I am a Jew).

I am enjoying myself enormously. I drive away thinking about the things Nicky said. I play them over in my mind. But by the time I arrive home and then watch ER, my mini-epiphany has all drained away, and I go back to normal. I cannot imagine how any of my fellow agnostics will possibly be converted by the end of the course.

As the weeks progress, the timetable becomes routine. Dinner, a talk from Nicky, coffee and digestives, the small groups. But the hostile questions have now become slightly less combative. One agnostic, Alice, who is the financial manager of an Internet company and rides her horse every weekend in Somerset, admits to taking Nicky's pamphlets away with her on business trips. She says she reads them on the plane and finds them comforting. We talk about the excuses we give our friends for our weekly Wednesday night absences. Some say they're learning French. Others say they're on a business course. There is laughter and blushing. I miss Week Three because I am reporting on wife-swapping parties in Paris. On Week Four, Nicky suggests I tell the group all about wife-swapping. The group asks me lots of questions. When I fill in the details, Nicky shakes his head mournfully. "What about the children?" he sighs. "So many people getting hurt." He's right. Nicky ends the night by saying to me: "I think it's important that you saw something awful like that midway through Alpha."

Week Five, and Nicky is onstage talking about answered prayers and how coincidences can sometimes be messages from G.o.d. He says he keeps a prayer diary and ticks them off when they are answered. As Nicky says these things, I think about how my wife and I were told we couldn't have a baby. We went through fertility treatment for four years. Every month was like a funeral without a corpse. And then we did have a baby, and when Joel was born I thought of him as a gift from G.o.d.

The moment I think about this, I hear Nicky say the word "Joel." I look up. Nicky is quoting from the book of Joel: "I will repay you for the years the locusts have eaten."

Later, I tell the group what happened. "Ah," they say, when I get to the part about us having a baby. "Ah," they say again, when I get to the part about Nicky saying "Joel," and then reading out an uncannily appropriate quote.

"Well?" I say.

"I don't know." Nicky smiles. "I think you should let it sit in your heart and make your own decision."

"But what do you think?" I say.

"If I had to put a bet on it," he says, "coincidence or message, I'd say definitely, yes, that was a message from G.o.d."

The subject is changed.

"So?" says Nicky. "How was everyone's week?"

Tony sits next to Alice. He is the most vociferous agnostic in the group. He always turns up in his business suit, straight from work, and has a hangdog expression, as if something is always troubling him.

"Tony?" says Nicky. "How was your week?"

"I was talking to a h.o.m.os.e.xual friend," says Tony, "and he said that ever since he was a child he found himself attracted to other boys. So why does the Church think he's committing a sin? Are you d.a.m.ned if you commit a s.e.xual act that is completely normal to you? That seems a bit unfair, doesn't it?"

There is a murmur of agreement from the group.

"First of all," says Nicky, "I have many wonderful h.o.m.os.e.xual friends. There's even an Alpha for gays running in Beverly Hills! Really! I think it's marvelous! But if a pedophile said, 'Ever since I was a child I found myself attracted to children,' we wouldn't say that that was normal, would we?"

A small gasp.

"Now, I am not for a moment comparing h.o.m.os.e.xuals with pedophiles," Nicky continues, "but the Bible makes it very clear that s.e.x outside marriage, including h.o.m.os.e.xual s.e.x, is, unfortunately, a sin." He says he wishes it wasn't so, but the Bible makes it clear that gay people need to be healed.

"Although I strongly advise you not to say the word 'healed' to them," he quickly adds. "They hate that word."

The meeting is wound up. Nicky, Pippa, and I stay around for a chat. We talk about who we feel might be on the cusp of converting. My money is on Alice.

"Really?" says Nicky. "You think Alice?"

"Of course," I say. "Who do you think?"

"Tony," says Nicky.