The Causeway Bay Books disappearances are a series of international disappearances concerning five staff members of Causeway Bay Books, located in Causeway Bay, Hong Kong. Starting October 2015, five staff of Causeway Bay Books have gone missing. At least two of them disappeared in mainland China, one in Thailand. One member was last seen in Hong Kong, but apparently had found his way to Shenzhen, across the Chinese border, without the necessary travel documents.
There was widespread suspicion that the booksellers were in detention in mainland China,[1][2] and in February 2016Guangdong provincial authorities confirmed that they had been taken into custody in relation to a case involving Gui Minhai.[3] There was muted response to the October disappearances, as unexplained disappearances and lengthyextrajudicial detentions are known to occur in mainland China.[4] 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 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".
The disappearances were followed by virtual appearances by two of the missing men, Lee Bo and Gui Minhai, in the form of letters and photographs in the case of the former and a confessional video from the latter broadcast on national television, in which they insisted their return to mainland China was indeed voluntary but which failed to account for their movement across national borders. These efforts were considered by commentators as farce or a charade, as they failed to satisfy citizens' concerns over their personal safety and the international community's concerns over the breach of "one country, two systems".
From:https://en.wikipedia.org/wiki/Causeway_Bay_Books_disappearances