He studied microexpressions and applied psychology at an unspecified university in the United States for half a year before returning to Hong Kong as West Kowloon Police Department's new CID senior inspector.
Hok-sum, however, does not seem to mind Chow Fun's obvious lack of respect and continues to peacefully and productively work with the unit members.
Kristal Tin portrays Phoenix Yip Chin-ting (葉展婷), nicknamed Ma-dam, the unit's Station Sergeant.
Her husband, Raymond, files for divorce due to irreconcilable differences, and applies for full custody of their son, Jacky.
Bosco Wong portrays Trevor Ho Lai-yin (何禮賢), nicknamed Chow Fun, the unit's Sergeant.
Aimee Chan portrays Perlie Ching Bui-yee (程貝兒), Hok-sum's younger half-sister who works as a public relations specialist at the police department.