For nearly a decade, the burly son of a poor family in rural Jiangsu was one of the most powerful men in China.
Today, the 71-year-old Zhou Yongkang is no longer an esteemed leader but a detainee of the party's anti-graft agency.
The abrupt turn came in December when Zhou was detained with his wife, Jia Xiaoye, in Beijing, sources said earlier.
Top leaders of the Communist Party had reached a consensus last August to purge their former high-ranking comrade, who was once a member of the Politburo Standing Committee and the country's security tsar.
The details of the allegations against him remain unclear, but Zhou could become the highest-profile trophy for President Xi Jinping, who is making his name as a fearless - some would say ruthless - crusader against corruption, willing to break an unspoken party taboo in punishing one of the elite for economic or social crimes.
The eldest son of a family in Xiqiantou village in Wuxi, Jiangsu province, Zhou escaped the rigours and poverty of farming life by receiving good grades at school and passing the national university entrance exam. Three years after entering Suzhou Middle School in 1958, he enrolled in the Beijing Petroleum Institute, now called the China University of Petroleum.
That educational experience obviously still resonates with Zhou, as his only two public appearances after retiring from political life in November 2012 were at his alma maters. After he visited last April, the Suzhou school said on its website that Zhou had "a unique feeling" for the school because it "had a profound effect on his life".
Before that visit, many of his associates - including Guo Yongxiang , secretary of the Political and Legislative Affairs Committee of the party's Central Committee - had been investigated for corruption. This lent credence to widely circulating rumours that Zhou would also be implicated.
In his last public appearance, in early October, Zhou - who graduated from the petroleum institute in 1966 having majored in geophysical surveying and exploration - spent all morning on campus as the school celebrated its 60th anniversary. He voiced strong support for Xi during the visit, urging teachers and students to uphold party unity.
But that effort was probably too little, too late. Zhou had been a patron of Bo Xilai, who was jailed for life in September for corruption and abuse of power.
Bo's fall from grace, and that of his convicted murderer wife Gu Kailai, was China's most dramatic political scandal since the trial of the Gang of Four after the Cultural Revolution.
It was inevitable the Bo investigation would soon ensnare Zhou - a dramatic fall for a man who started his career as a technician at the Daqing oilfield in Heilongjiang . What is now China's biggest base for refining pretroleum had only been in service a few years before Zhou arrived. He moved on to work in the Liaohe Oilfield and kept rising through the industry's ranks.
"Zhou plunged into the work at the oilfield with great zeal," said a person with close ties to the industry who spoke on condition of anonymity. "He was a natural leader. The winter in northeastern China is long and cold, but he led from the front and … never left his subordinates alone."
Zhou had a reputation for being a hardy and fearless worker, but was very generous, the source said.
"The living conditions were poor at the time, and workers didn't get enough to eat," he said. "Zhou was also poor but often brought steamed buns from home for his co-workers."
Zhou later became the head of the Liaohe oil sector and developed a relationship with former vice-president Zeng Qinghong , who was then on the national energy committee.
In 1996, Zhou became head of the China National Petroleum Corporation (CNPC), now the nation's largest oil producer.
Most of Zhou's top aides from the oil sector days have also been detained, including Li Hualin , CNPC's vice-general manager and Zhou's former personal secretary. Some of Zhou's relatives are also under investigation for alleged unlawful deals involving CNPC, including eldest son Zhou Bin , daughter-in-law Huang Wan , brother Zhou Yuanqing , sister-in-law Zhou Lingying and her son Zhou Feng.
Jiang Jiemin , former CNPC head and another Zhou protégé, was questioned by the Central Commission for Discipline Inspection, the party's anti-graft watchdog, in 2012 over payments to silence families of victims in a Ferrari crash in Beijing that also claimed the life of the only son of Ling Jihua , the former top aide to former president Hu Jintao . Jiang was later expelled from the party and is under investigation.
In 1999, Zhou became the party chief of resource-rich Sichuan province, continuing to gain more followers. He was appointed minister of public security in 2002 and five years later became one of the nine members of the 17th Politburo Standing Committee, the party's most senior decision-making body that also included Hu, Xi and their respective premiers Wen Jiabao and Li Keqiang .
As the domestic security tsar, Zhou unveiled a host of measures to boost the relationship between the police and the public, aimed at easing social tensions. His quotes were posted in police stations across the country.
But things did not go entirely to plan. In 2008, a 28-year-old named Yang Jia killed six police officers in Shanghai and became a celebrity on the internet among those who disliked Zhou's methods. Zhou, however, remained popular among policemen.
The net continued to close around Zhou at the end of last year. Li Dongsheng , a former deputy security minister and Zhou ally, was detained in late December. Shortly after, Beijing city's spy chief Liang Ke was detained and later sacked on suspicion of massive corruption. Other sources have said Liang had assisted Li and Zhou to monitor the phone calls of party elites.
Historian Zhang Lifan said the investigation into Zhou showed factional struggles within the party were intensifying.
"We need to watch whether the struggle stops with Zhou. Xi might have won the ultimate victory, and it could stop there," Zhang said. "After all, such a struggle is hurting the party, too, because it reveals to the public so many ugly things."
Additional reporting by Zhuang Pinghui