NEW YORK — "In God's Name" begins with a brief introduction from its filmmakers, Jules and Gedeon Naudet, who take the viewer back — back to the morning of Sept. 11, 2001, when the brothers were in lower Manhattan working on a documentary on New York firefighters.

Jules was shooting inside the World Trade Center's north tower when the south tower fell. Gedeon spent hours fearing his brother was lost. Jules feared the same about Gedeon.

This all became part of their film, "9/11," which premiered on CBS in March 2002 and was subsequently seen around the world.

But years later, the film, and the awful day that dominated it, still absorbed them.

"It was the first time I had been confronted with death," Jules says, "and I had questions, existential questions. What does it all mean? I remember talking with my brother: Is there something we can do with this in a documentary?"

The plan they hatched called for taking their questions to people well-positioned to address them: a dozen of the world's leading spiritual figures, representing some 4 billion followers.

The Naudets' wish list included Pope Benedict XVI, head of the Roman Catholic Church, and the Dalai Lama, spiritual leader of Tibetan Buddhists — not the sort of folks normally subjected to a pop-in from an inquiring film crew.

But the Naudets believed they could get access. And not just for an interview, but for a behind-the-scenes glimpse into the personal lives of these public figures.

Turns out the brothers were right. The two-hour "In God's Name" (8 p.m. MST Sunday on CBS/Ch. 2) is a crash project still being completed. But the parts available for preview hold promise of a beautifully realized portrait of faith in a dozen human variations. For all its elements, it flows seamlessly with images and ideas that should awaken the viewer to new possibilities.

As with "9/11," the Naudets have again collaborated with veteran CBS News producer Susan Zirinsky and her team — who received the brothers' 180 hours of footage just four months ago.

How to cull this mass of material? How to give it form?

"In God's Name" provides mini-profiles of each leader, but the main throughline is a collective day-in-the-life shared by all its subjects.

"The idea is to show the things that unite us, rather than divide us, and to give a sense of progression through the day — and through the questions we ask," says 34-year-old Jules, who, with his 37-year-old brother, was born in France but moved to New York with their family in their teens.

"I think after 9/11," says Zirinsky, "everybody had kind of the same questions: Why are we here? Does God exist? How could God let that happen?"

But she adds a caveat as to what the film is not. "It's not a tutorial on each religion. These leaders represent their religions, and are here with their thoughts on life and purpose and prayer and the existence of God."

Though months were required in some cases, the Naudets landed the cooperation of each of the dozen leaders they originally sought (including the pope and the Dalai Lama):

Alexei II, patriarch of Moscow and head of the Russian Orthodox Church; Ayatollah Muhammad Hussein Fadlallah, a prominent Shiite Muslim leader; Mark Hanson, presiding bishop of the Evangelical Lutheran Church in America and president of the Lutheran World Federation; Michihisa Kitashirakawa, jingu daiguji (high priest) of the Shinto Grand Shrine of Ise. Also: Yona Metzger, Ashkenazi chief rabbi of Israel; Frank Page, president of the Southern Baptist Convention; Muhammad Sayyed Tantawi, sheikh of Al-Azhar and a prominent Sunni Muslim leader; Joginder Singh Vedanti, jathedar of the Akal Takht, the Sikhs' highest authority; and Rowan Williams, archbishop of Canterbury and head of the Church of England. And the only woman in the group: Amma (Mata Amritanandamayi), a Hindu spiritual leader.

To visit them, the brothers (with a six-person crew) journeyed to Egypt, England, India, Israel, Japan, Lebanon, Russia and the Vatican, as well as Illinois and South Carolina, between October 2006 and last June.

Asked if he and his brother were naive to have ever conceived such a project, Jules laughs, and agrees: "Completely! I think, strangely enough, that is why these people said yes. I think our naivete convinced them that we were for real."Says Zirinsky: "It's kind of like these two guys went knocking on the door of 12 of the world's most influential spiritual leaders and said, 'Excuse me, could we peek in?' And they all said, 'Yeah, c'mon in."'

What was waiting inside? -->

"I did not find God during the journey," says Jules. "And I can't say I found the meaning of life. But I found that we all have to find our own meaning for life. Now I have a good start."