One of five Hong Kong booksellers who disappeared last year says he was forced by Chinese agents into a confession of "illegal trading".
Lam Wing Kee was seized in the Chinese city of Shenzhen last October.
He and the four other men worked at a publishing house that sold books critical of China's leaders.
Mr Lam said a confession broadcast on Chinese television in February, featuring four of the men, had been scripted.
"It was a show, and I accepted it," he told a news conference on Thursday, according to the South China Morning Post.
"They gave me the script. I had to follow the script. If I did not follow it strictly, they would ask for a retake."
Four of the men from Mighty Current publishing house, Mr Lam, Gui Minhai, Lui Bo and Cheung Jiping, gave details of their alleged offences during their appearance on Phoenix TV in February.
Lam Wing Kee returned to Hong Kong on Tuesday. Only one of the men has yet to return from the mainland.
Some people in Hong Kong believe the four were detained by China because of a book about President Xi Jinping.
They said they had sold 4,000 "unauthorised" books to 380 customers in mainland China, Phoenix TV reported.
Mighty Current publishing house disappearances
1. Lui Bo, general manager. Went missing: Shenzhen, 15 October 2015 Returned: March 2016
2. Cheung Jiping, business manager. Went missing: Dongguan, 15 October Returned: March 2016
3. Gui Minhai, co-owner. Went missing: Thailand, 17 October Still missing
4. Lam Wing Kee, manager. Went missing: Shenzhen, 23 October Returned: June 2016
5. Lee Bo, shareholder. Went missing: 30 December - he says from the mainland, Mr Lam says it was from Hong Kong Returned: March 2016
Public confessions have long been a part of China's criminal law, but experts say many confessions are forced.
In the news conference, Mr Lam also said:
- he was arrested in Shenzhen, a southern city on the mainland, before being held overnight
- he was then blindfolded and put on a train for up to 14 hours to the city of Ningbo
- while there, he was kept in a small room by himself, and made to sign a document agreeing he would not contact his family or a lawyer
- the Chinese authorities had asked him to return to the mainland and hand over disks containing the names of people who had bought the books - he said he would not now do so
- he spoke out as he was the only one of the five men with no relatives on the mainland. "If I myself, being the least vulnerable among the five booksellers, remained silent, Hong Kong would become hopeless," he said
The defiant bookseller's bombshell revelations electrified the journalists in the room, as well as social media in Hong Kong.
At the scene: Juliana Liu, BBC News, Hong Kong
No-one had expected him to tell all.
Besides Gui Minhai, who remains in custody, Mr Lam was the last of the associates of the Mighty Current publishing house to be released from detention.
The others - Lee Bo, Lui Bo and Cheung Jiping - had all been released much earlier and said little about their time in mainland China.
They had all decided it was better, perhaps safer, to stay silent.
But Mr Lam chose a different route.
He decided to take a public stand, he said, because he wants Hong Kong people to defend the system that separates this city from China.
Under Hong Kong law, Chinese police do not have jurisdiction in Hong Kong, which is governed under the principle of "One Country, Two Systems".
But the case has sparked international concern that China could be attempting to rein in freedom of expression in Hong Kong.
China's foreign ministry said its officials would not behave illegally and urged other countries not to meddle in its affairs.
Hong Kong's government said in a statement "that the police are now proactively contacting Mr Lam himself to understand more and will take appropriate follow-up action".
It added that any evidence of intervention by Chinese law enforcement agencies in Hong Kong would be "unacceptable".
"Lam Wing Kee has blown apart the Chinese authorities' story," Mabel Au, director of Amnesty International Hong Kong, said.
"He has exposed what many have suspected all along - that this was a concerted operation by the Chinese authorities to go after the booksellers."