BEIJING -- Just months before his fall from power, Bo Xilai asked the brother of his first wife to meet him at a government compound in the southwest metropolis of Chongqing.
Mr. Bo, the city's Communist Party chief, pointed to a stack of papers and said he had forensic reports that proved the existence of a continuing plot to poison his second wife, Gu Kailai. Then he asked the other man to step into the yard and turn off his cellphone. The person suspected of masterminding the scheme, Mr. Bo said, was his son from his first marriage, Li Wangzhi, also known as Brendan Li, a graduate of Columbia University who was working in finance in Beijing.
"Could this be true?" Mr. Bo asked. When the brother-in-law insisted the fears were outlandish, Mr. Bo seemed relieved.
The story, recounted in two recent interviews with Mr. Bo's estranged first wife, Li Danyu, 62, deepens the Shakespearean dimension of a scandal that has gripped this nation and disrupted the party's once-a-decade leadership transition.
The Bo saga has already shown that the rise and fall of a politician in China can hinge as much on family intrigue as on political battles.
In dynastic eras, palace upheavals were often catalyzed by paranoia and jealousies within the imperial family. From Qin Shihuang, the first emperor, to the Empress Dowager Cixi to Mao Zedong, China's rulers have tended to suspect conspiracies against them and their close kin and have looked for assassins in the shadows. The same fears can arise within aristocratic Communist families today, especially among those vying for leadership positions.
Until his downfall, Mr. Bo was considered a contender for a top post during the handover of power that is taking place this autumn. But those hopes were dashed last spring when he was detained.
On Sept. 28, the party announced it was expelling Mr. Bo, 63, and would prosecute him on a range of criminal charges. Ms. Gu, 53, has been convicted of murdering a British business associate, Neil Heywood; in a twist on the earlier suspicions, Ms. Gu confessed to poisoning him last November because she thought he was a threat to her son, according to officials.
In the interviews, the first she has given to a news organization, Ms. Li spoke in detail about her marriage to Mr. Bo, giving a rare glimpse into the early life and thoughts of the son of a revolutionary leader and someone whom Ms. Li described as an idealist enamored of communism.
"We believed we needed to save the rest of the world from the hell of capitalism," she said.
Ms. Li, also a "princeling" child of a party official, said that although there has been a long history of enmity between her and Ms. Gu, her son never conspired to murder Ms. Gu.
Another family member confirmed that Ms. Li's brother had met with Mr. Bo and had been told of the alleged plot. He also insisted the son was innocent. The son and his uncle both declined to comment. Mr. Bo and Ms. Gu are under detention.
Although she has no proof, Ms. Li said she suspected Ms. Gu was the one who first blamed her son for the perceived murder plot, and the so-called forensic evidence might have been provided by Wang Lijun, the former police chief convicted of helping cover up Mr. Heywood's murder. Ms. Li said she feared Ms. Gu wanted to have her first son arrested or harmed.
"She can be that paranoid," Ms. Li said. As for Mr. Bo, she said, he was "good in nature and didn't want to believe this evidence."
Ms. Li spoke with nostalgia of her romance with Mr. Bo, which began when the two met in 1975, at the end of the Cultural Revolution. Ms. Li said she did not stay in contact with Mr. Bo after their bitter breakup in 1981.
The web of entanglements among the families reflects the insular nature of China's "red nobility." Ms. Li's older brother, Li Xiaoxue, is married to Ms. Gu's older sister, the daughter of an army general.
It was this brother who met last October, weeks before Mr. Heywood's death, with Mr. Bo in Chongqing.
Li Xiaolin, a lawyer associated with Ms. Gu and no relation to Mr. Bo's ex-wife, said in a telephone interview that Ms. Gu and her family members believed she had been poisoned years earlier with a heavy metal substance.
He said that he did not know whom she blamed for the poisoning. Mr. Li said that Ms. Gu's shaking hands, evident at the trial in August, were a result of the poisoning. Ms. Gu had even taken up knitting on her doctor's advice to try to regain control of her hand muscles, he said.
Several people close to Mr. Bo's family said they had heard Ms. Gu was poisoned at one time, and that there was extreme paranoia within the household in recent years. But three family friends who spoke on the condition of anonymity said they did not believe Ms. Gu was fabricating evidence about Ms. Li's son. They said Ms. Li had long resented Ms. Gu and waged private attacks against Mr. Bo and Ms. Gu to discredit them.
Ms. Li and Mr. Bo, whose elite families had known each other for years, began their love affair in 1975. Mr. Bo had just endured years of prison during the Cultural Revolution, when his father was purged, and was working in a factory.
Ms. Li, whose family had also suffered, was working as a military doctor. "What he did a lot was he read the selected works of Marx and Lenin," Ms. Li said. "He was a simple and progressive young man."
Living in different cities because of their jobs, they wrote letters to each other every three days. In a poem, Mr. Bo ends with lines that reflect both political fervor and romantic feelings:
Raise the army banner,
And laugh still more, gazing at the red cosmos,
Spare no effort to move forward.
Ms. Li's first name means "red cosmos." They were married in September 1976 and had a son the next year.
Mr. Bo enrolled in Peking University. He tried to read eight pages of English each day from library books, she said. He told her, "Eventually China will open to the world, so we have to learn."
The two moved into Zhongnanhai, the Beijing leadership compound, after Mr. Bo's father became a vice premier. But Mr. Bo did not aspire to join those ranks, Ms. Li said. Mr. Bo switched from studying history to journalism.
The end of the relationship began on their son's fourth birthday, June 20, 1981. Mr. Bo surprised Ms. Li by asking for a divorce. "He felt very sad and cried and hugged us," she said. That night, he told her, "I have no feelings for you anymore."
Ms. Li refused to grant the divorce, though she moved out of Zhongnanhai. The case went to court. The divorce was completed in 1984. Ms. Gu, in a book she wrote, said she met Mr. Bo that year in Dalian. But Ms. Li said Mr. Bo might have been secretly seeing Ms. Gu when the two were at Peking University, while Mr. Bo was still married.
To try to stop the divorce, Ms. Li told officials that Ms. Gu had destroyed the marriage. In the interviews, Ms. Li said Ms. Gu, a lawyer, had threatened legal action if Ms. Li persisted.
Ms. Li said she "finally summoned enough courage to tell my story" after being contacted by this newspaper. Now, she and her son await the party's final verdict on Mr. Bo.
"In those early years it was pure love," she said. "Even though he didn't see me for 30 years, I forget the bad things and remember the good. You don't want to live with hate."
Mia Li, Xu Yan and Amy Qin contributed research.
This article originally appeared in The New York Times.