It was among a string of disappearances, all linked to a bookstore in downtown Hong Kong.
Causeway Bay Books is now empty and unattended, but for years it published books on Chinas leaders, and other material considered transgressive by Chinese authorities and banned in the mainland.
Around the same time that Gui disappeared, two other men associated with Causeway Bay Books - Lui Por and Cheung Chi Ping - also vanished after crossing into mainland China.
As it stands, Cheung Chi Ping, Lam Wing Kee and Lui Por have all been released and returned to Hong Kong, but the whereabouts of Gui Minhai is unknown. He has not been seen since the last video he appeared in, in February.
His daughter Angela is demanding answers, but will she ever get them?
