Three people charged with blackmailing and falsely imprisoning a woman appeared in North Kowloon Court yesterday. Prosecutor Angus Lee said karaoke club manager Yam Chui-ngai, 32, engineer Chu Wai-keung, 32, and club manager Wong Siu-chu, 33, stopped a woman on a Mongkok street on April 6. He said they believed she knew about money they claimed to be owed. It was alleged the trio kept the victim in a Mongkok flat against her will and forced her to sign IOUs. It was also alleged Wong and Chu forced the woman into prostitution. All three were denied bail by magistrate Maria Yuen Ka-ning and will return to court on May 8. No pleas were taken.