A mansion mysterious enough to warrant a book lies behind a forest of trees and down a long, winding driveway at 104 Dans Highway in New Canaan.

In "The Mysterious Life of Huguette Clark and the Spending of a Great American Fortune," by NBC News investigative reporter Bill Dedman and Paul Clark Newell Jr., a distant relative, the life of Huguette Clark, the exceedingly unusual millionaire heiress who owned the home, is put together piece by piece.

What comes out is the story of a reclusive woman of fabulous wealth who did not speak with outsiders, whose best friends were intricately designed dolls and who lived the last 20 years of her life in a hospital room, though she was, for the most part, in perfect health.

In 2009, Dedman was researching homes in Connecticut for an upcoming move. Out of curiosity, he began searching online for listings of the most expensive houses.

At a listing price of $24 million, down from $34 million, Le Beau Chateau was the most expensive in the state. When he found a note in the listing that the house had been unoccupied for the 60 years Clark owned it, he drove there the next day to investigate how that could be.

When Dedman arrived at 104 Dans Highway he met the caretaker at the iron fence, which blocks the entrance to the long driveway that leads up to the house.

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"It was so surprising to me that he was asking me questions," Dedman recalled. "I said, `I don't know anything.' All he knew was that he got paid by (Clark's attorney Wallace Bock) every month. He was asking me, `Do you think she died?' I said, `I don't know.'"

Dedman said he dug around in public records and visited Clark's apartment in Manhattan, where he met the doorman, who told him Clark had not been there in 20 years. So Dedman went to his editors at NBC News and pitched them the story, which he said was outside of his typical investigative beat.

"My editors said, `I would read that,'" he remembered. And thus, the series, and eventually the book, were born.

Clark was the youngest daughter of William Andrews Clark, a Gilded Age tycoon who made his fortune in the copper industry. She was born in Paris in 1906 and spoke English with a slight French accent. She grew up in a 121-room mansion on Fifth Avenue and 77th Street in Manhattan. She was married for a little more than a year, in 1928, and never remarried, though her letters show she kept in touch with her ex-husband throughout his life. When her mother died in 1963, it seems Clark, who never was very social, began retreating further. She stopped visiting the palatial family vacation home, Bellosguardo, in Santa Barbara, Calif., after her mother died. The home, which is situated on a cliff overlooking the Pacific Ocean, still has two cars, a 1933 Cadillac limousine and a 1933 Chrysler Royal Eight convertible, sitting unused for decades, in the garage, according to the book.

Dedman believes Huguette Clark bought the New Canaan home in 1951, in part, as a bomb shelter in case of a Cold War attack. The walls are very thick, and the house could have provided a country retreat.

From the early 1950s to 1991, she lived in isolation in her apartment on Fifth Avenue. From 1991 to her death in 2011 at the age of 104, she lived in private rooms at Doctors and Beth Israel hospitals. Through her 90s and into her second century, Clark did not even take the rounds of pills typical of people at that age. It was clear she was in the hospitals only because she wanted to be, according to the book. She rarely spoke in person to anyone but her personal caretaker and her lawyers, though she did keep up correspondences by mail, and by phone with some people, including Newell, who helped Dedman with the book and is listed as the co-author. Though she kept in touch with Newell, he never once called her, or had her number. She would call him every couple of months and try back later if he wasn't home. Snippets of those conversations are included in the book.

Since her death, her estate has plunged into a legal battle between her distant relatives and her aides, and the fate of her New Canaan home remains uncertain.

Since 2001, Dedman, who won the 1988 Pulitzer Prize for his series "The Color of Money," which uncovered racial discrimination in the lending of money for homes in Atlanta, has written dozens of articles about Clark for the NBC News website.

A year and a half ago, he began work on the book with Newell. At 359 pages (456 with end notes), the book is meticulous with its details. He was never able to interview Clark, and a request made through her lawyers was denied. Instead, he was forced to put her life together through public records, contemporaneous newspaper clippings, some of the records Newell had recovered, and tireless research, including reaching out to those who knew her.

"In a way, what it is, is the history of the country," Dedman said in a recent interview. "Huguette's father was born in 1839 and she lived until 2011 -- that takes you from the eighth president (Martin Van Buren) to Obama. If you go back to his father, he was born the same year George Washington gave up the presidency."

The first third of the book deals with Huguette's tycoon father, William Andrews Clark, who grew up in a cabin in western Pennsylvania, struck out for the California Gold Rush, and ended up becoming a copper magnate in Montana. Incredibly wealthy but unable to break into old money social circles of New York, the man spent outrageous sums of money on homes and art. Clark was at the center of a brazen bribery scandal. In his 1899 run for the U.S. Senate, Clark's associates were found to have distributed envelopes containing $10,000 to buy the votes of state representatives in his bid for the seat. He was found out and disgraced, but ran again for the seat two years later and won. He served in the Senate from 1901 to 1907.

A significant part of the book is comprised of descriptions of the astounding wealth of the Clark family.

"Reporters who toured the home counted 26 bedrooms, 31 bathrooms, and five art galleries," Dedman wrote, describing the 121-room house in Manhattan. "Below the basement's Turkish baths, swimming pool, and storage room for furs, a railroad spur brought in coal for the furnace, which burned seven tons on a typical day, not only for heat but also to power dynamos for the two elevators, the cold-storage plant, the air-filtration plant, and the 4,200 light bulbs."

Dedman, who ended up moving to Westport, allowed that there is an aspect of voyeurism into the lifestyles of the wealthy.

"There's no doubt. It's definitely part of the American character to want to know what it's like in those houses that you can't afford to live in," he said. "That's at the root of this, and the woman turned out to be interesting, but what drove this and my initial interest is this astonishing idea that while the rest of us are striving to pay our mortgage or rent, here are people who can afford to own mansions outright and afford never to use them. That's much more interesting. If Oprah has four houses, I don't care much. If you told me Oprah owned a house for 50 years and never visited it, that's crossed from, `That's what rich people do' to `Even rich people think it's odd.'"

In thinking about the book, Dedman recalled two events in his life that may have influenced him toward undertaking the project. One was Advanced Placement U.S. History, in which he loved the stories and research projects. Another was going through his grandmother's attic several years ago, after she died, and finding artifacts from her life, including her checkbook and hat collection. He said tangible items like those can offer a window into a individual's personality and life.

"I wanted it to have a little of a scrapbook feel, so that you could feel that you went through (Huguette's attic)," he said. "And it did appeal to me as a vehicle for exploring the times. There's the Titanic, Rockefeller, Twain, Lindbergh, so that you have the whole history of the country laid out through one daughter and her parents."

twoods@bcnnew.com; 203-330-6582; @Woods_NCNews