In a Beijing complex with the Orwellian name Freedom City, I visited dissident Hu Jia on Dec. 20. He and wife Zeng Jinyan seemed upbeat, still euphoric over the birth of their daughter Qianci in November. The couple thought the infant's arrival had won them some breathing room, since the guards usually stationed inside their apartment building now seemed less obtrusive. "Maybe the birth of our baby gave them a dose of morality," said Hu, 34, eyes twinkling wryly.

Pouring me a cup of tea, he described how security personnel had kept him and Zeng, also an activist and blogger, under de facto house arrest for more than 200 days. The agents congregated in the hallways or lounged on makeshift plywood cots perched on the cramped stairway landings leading to Hu's fourth-floor apartment. "They would be chain-smoking or playing cards or sleeping. It was like an airport waiting room. My poor neighbors!" (Hu had also been detained and held incommunicado for 41 days in early 2006, during which time Zeng blogged about their plight.) But on that wintry afternoon his captors were nowhere to be seen as I trudged upstairs with a photographer. Hu and Zeng introduced me to Qianci, tousle-haired and sleepy, while posing for photographs. He speculated, "If it weren't for the Olympics I'd be behind bars now."

A week later, he was.

On Dec. 27, Hu was at his computer when two dozen police officers swiftly entered the apartment and hustled him away, confiscating laptops, cell phones, books and bank cards. My visit was apparently the last time Hu and Zeng were interviewed face-to-face and photographed by foreign media before his arrest.

Hu and Zeng are a special breed of Chinese activist. Unlike some, they have embraced an unusually diverse range of political causes. Beginning in 1996, Hu's early activism focused on the threat of desertification and China's fragile ecosystems, especially in Tibet, where he supported tree-planting campaigns and protection of the endangered Tibetan antelope, or chiru. A vegetarian, Hu is best known for founding the HIV/AIDS support group Loving Source. He met Zeng when they were volunteers working on HIV/AIDS issues.

Through e-mail and Internet phone services such as Skype, Hu and Zeng networked with human-rights activists across a wide spectrum. Freedom of the press. Legal and civil rights. Assisting victims of forced evictions and rural land-grabs brought on by China's tsunami of demolition and redevelopment. Hu's moment of awakening was the carnage of the 1989 Tiananmen crackdown on prodemocracy protesters. "I nearly went crazy, asking, 'How could this happen?'" he told me. "That's when I turned to Buddhism, which opposes all killing."