Lam Wing-kei, a slight, soft-spoken man who carries a satchel and looks extremely tired, doesn't look like much of a threat to the ruling Chinese Communist Party.
But he is the only one of five detained booksellers to defy Beijing by speaking in public about his interrogation at the hands of a special task force of state security police directly commanded by the highest level of the Chinese government.
Members of this secret task force ensured that he was picked out of an incoming crowd at the Lo Wu border checkpoint last October, before blindfolding him and whisking him to an interrogation room in Ningbo, a nightmare 10 hours' drive away.
"I'm sure that they are following me since my return to Hong Kong; that's for certain," Lam told RFA in an interview on Monday.
"If the Hong Kong government asks me, I can point them out on security video, because it will exist from the border crossing."
But Lam has lost any confidence that the government of Hong Kong will stand up to Beijing, despite being promised separate status as a law enforcement jurisdiction under the terms of the city's 1997 handover from former colonial ruler Britain to China.
"I don't even know if they would detain those people, or what they would do with them, even though I would be able to identify them," he said, nervously twisting a paper teacup as he spoke to RFA's Cantonese Service.
"I don't think they'd do anything much at all, because they haven't any jurisdiction to detain officials from the mainland. All I can do is offer proof," Lam said.
Lam says he has already endured months of questioning, mostly about which Chinese citizens were buying books from the Causeway Bay store and its sister imprint Mighty Current.
As President Xi Jinping rallies officials to fight back against "hostile overseas forces" thought to be trying to overturn the regime with imported notions of democracy, the rule of law, and religious freedom, places like Causeway Bay Books, purveyors of sometimes sensationalist gossip about Chinese politics and political elite, are first in the firing line.
After failing to provide his interrogators with enough detail to satisfy them, Lam was sent back to Hong Kong and told to follow the same script as three of his former colleagues at the now-shuttered Causeway Bay Books store, whose database of customer details he was charged with bringing back to China.
Like his colleagues Lee Bo, a British passport holder, Lui Por, and Cheung Chi-ping before him, Lam's first port of call in the former British colony was a police station, where instead of filing a complaint about his treatment by the Chinese authorities, he merely requested that they close his missing persons file.
Lam had then intended to comply with his interrogators' demands, but something stopped him in his tracks.
According to him, it was the knowledge that some 6,000 people had turned out in angry protest over the presumed detention of him and his colleagues, who also include Swedish national Gui Minhai, the only one of the five not to re-emerge after "helping police with their inquiries."
So he held a press conference instead to tell his story, before leading another march of several thousand supporters to Beijing's Liaison Office in Hong Kong on Saturday, all chanting his slogan "Say no to power!"
"I am doing this both for myself, and for the people of Hong Kong," Lam said, when asked why he hadn't played along like the others.
"I have seen a lot of commentary that is very funny, including people saying that my political background shows that my actions were politically motivated," he said.
"They're just grasping at straws, trying to muddy the waters so as to cover up their own covert operations."
As Lam stood up in front of the city's Legislative Council to tell his explosive story to lawmakers, pro-Beijing media entered the fray with a series of interviews and rebuttals from his colleagues.
Lam's assertion that Lee Bo, who went missing from his place of work inside Hong Kong's internal border with mainland China on Dec. 30, was kidnapped by Chinese agents operating within the city's borders was denied by Lee himself.
His claim that his colleagues are being placed under intense pressure via loved ones in China was also rubbished in Hong Kong media outlets loyal to Beijing.
The city's Sing Tao Daily quoted a woman claiming to be a former girlfriend as saying that Lam wasn't denied legal representation, as he had told journalists.
It also published interviews with Lui Por and Cheung Chi-ping, who said their televised confessions weren't scripted, as Lam had described.
But Beijing has also moved to delete any mention of the booksellers' cases, defending their detentions on the grounds that the men were detained in China because they had broken Chinese law by selling banned books to its citizens, albeit from Hong Kong, where selling books isn't against the law.
Lam, who has described himself as "less burdened" than his colleagues, meaning that he is less susceptible to manipulation by China, said he is certain that Beijing is now merely trying to cover its tracks by throwing its weight publicly behind the narrative agreed with the other booksellers.
"I think they're the ones who are the conspirators," Lam said. "You can trace the provenance of their argument right back through comments from mainland officials and that article in the Global Times."
Beijing's powerful propaganda department last week ordered its tightly controlled media outlets to delete all mention of an article in the Global Times, which has close ties to the party, which tried to undermine Lam's story.
Lam says he won't take issue with this counternarrative any more.
"I think it could get [my colleagues] into trouble," he said. "But my account is the correct one, unless there's a problem either with my memory, or my powers of description."
Store manager and British passport-holder Lee Bo, 65, went missing from his workplace in Hong Kong on Dec. 30. He is now back in Hong Kong, but disputes Lam's account. The U.K. government has said he was "involuntarily removed" from the city in a breach of promises made by Beijing before the handover.
General manager Lui Por and colleague Cheung Chi-ping are also believed to have been detained during trips to China from their usual base in Hong Kong, and have also returned briefly to Hong Kong to cancel their missing persons cases.
Publisher and Swedish nation Gui Minhai left his Thai holiday home under opaque circumstances before appearing on state television CCTV "confessing" to involvement in a drunk-driving death 10 years earlier, a claim that his family have dismissed as highly dubious.
Gui's daughter Angela last week praised Lam's courage in speaking out, but called on the world not to forget that her father remains in illegal detention in China.
Reported by Lam Kwok-lap for RFA's Cantonese Service. Translated and written in English by Luisetta Mudie.