Causeway Bay Books disappearances

It was widely believed that the booksellers were detained in mainland China, and in February 2016 Guangdong provincial authorities confirmed that all five had been taken into custody in relation to an old traffic case involving one of the detainees, Gui Minhai. While response to the October disappearances had been muted, perhaps in recognition that unexplained disappearances and lengthy extrajudicial detentions are known to occur in mainland China, the unprecedented disappearance of a person in Hong Kong, and the bizarre events surrounding it, shocked the city and crystallised international concern over the possible abduction of Hong Kong citizens by Chinese public security bureau officials and their likely rendition, and the violation of several articles of the Hong Kong Basic Law. In his report to the British government and parliament in early January 2016, foreign secretary Philip Hammond said the incident was "a serious breach of the Sino-British Joint Declaration on Hong Kong and undermines the principle of one country, two systems".
Following the international focus on the disappearances, there were virtual reappearances by two of the missing men, Lee Bo, in the form of letters and photographs, and Gui Minhai, in a confessional video (widely regarded as being a forced confession) broadcast on national television, in which they insisted that their return to mainland China was voluntary but which failed to account for their movement across national borders. These efforts were widely derided by commentators as a farce and a charade, as they failed to satisfy concerns over the breach of "one country, two systems" and its practical and constitutional implications.
On 16 June 2016, shortly after he returned to Hong Kong, Lam Wing-kee gave a long press conference in the presence of legislator Albert Ho in which he detailed the circumstances surrounding his eight-month detention, and describing how his confession and those of his associates had been scripted and stage-managed. Lam indicated the involvement of the Central Investigation Team, which is under direct control of the highest level of the Beijing leadership. His revelations stunned Hong Kong and made headlines worldwide, prompting a flurry of counter-accusations and denials from mainland authorities and supporters. Provided by Wikipedia