Chen Mei was perhaps an unlikely hero of the coronavirus pandemic.

A shy but passionate zoology graduate, he worked for a non-profit that helps people with hearing loss, according to his brother Chen Kun. He loved cats and kept a low profile online, said a friend who asked not to be named out of fear of punishment from the authorities.

“He was never the initiator of projects — he always played the supporting role,” said Chen Kun.

But with Terminus 2049 he made an exception.

“You might have to be more cautious about this,” Chen Kun remembers telling his brother, reminding Chen Mei that if he could see his posts about Terminus 2049, then others could, too.

Even so, Chen Kun didn’t think his brother would be arrested as what he was doing was relatively conservative compared to other activists. But under China’s system of information control, the rules are always shifting.

It’s not always immediately clear where the red line is for censorship, and because the rules aren’t static, some people venture into gray areas in the belief that what they are doing will be tolerated by the government. They hope that they will be lucky enough to avoid censorship and potential punishment.

“It’s really unclear what is legal and what is illegal,” a friend of Chen Mei noted. “Why would archiving those articles be illegal?”

When Chen Kun got that fateful call on April 20 from his brother’s boss, he was in Indonesia, trying to avoid the pandemic. His brother Chen Mei had disappeared alongside Terminus 2049 co-founder, Cai Wei, and Cai Wei’s girlfriend, he soon learned.

A few days later, Cai Wei’s family received a phone call from the police, telling them Cai Wei had been arrested and was under residential surveillance at an undisclosed location. He was suspected of picking quarrels and provoking trouble — a charge commonly used to arrest activists in China. Those charges related to two things: building a website on a foreign server, and publishing inappropriate remarks online, Cai Wei’s father Cai Jianli said. That same day, Chen Mei called his boss and told him he would be out sick for a month.

At the beginning of May, Chen Mei’s parents received a notice via courier from police which confirmed their suspicions: their son was under residential surveillance at a designated location, a system whereby people can be held for up to six months without charge.

China’s Ministry of Foreign Affairs and State Council Information Office have not responded to requests for comment on case statuses of Cai Wei and Chen Mei, and fellow truthtellers Chen Qiushi and Fang Bin. They did not confirm how many people had been detained or prosecuted for sharing information on the pandemic. China’s Cyber Security Administration has not responded to a request for comment on whether archiving and republishing Chinese news reports is illegal.

Since September, Chen Kun has been living in self-imposed exile in Paris, where he is studying. He believes it is dangerous to return to China, as he has been vocal online about his brother’s disappearance.

Chen Kun had already spent time in detention in Beijing back in 2014. He said he was arrested after his girlfriend put up posters in the city supporting Hong Kong’s pro-democracy Umbrella Movement. Authorities believed he ordered her to do it.

“It wasn’t my plan to study in Paris,” he said. “I would have gone back to China after the pandemic if it weren’t for my brother.”

He worries for his family left in China, including his mother, who the Chinese authorities have contacted to ask about Chen Mei’s political activities, although she knew nothing.

“I’m worried, but I don’t have any choice. I just have one option which is to speak out,” Chen Kun says.

Chen Kun says if people can only see the “whitewashed” version of history promoted by the Chinese government, there will be no way to learn from this current outbreak.

“Then what was the sacrifice of this year for?” he says.