On-na and Hon-sam are assigned to newly established Cold Case Special Investigation Unit (CCSIU). The duo do not get along. Hon-sam vents this frustration on Chin-chiu as he realizes his team members are lethargic and do not care about their assignments. Some new clues are gathered in a cold case. CCSIU is investigating Mr and Mrs Wan’s missing daughter Ching-ching case. Tat-wah and Dan-gei take shelter in Yiu-chung’s place. They are assigned the task of guarding some remote minibus station. Because of this, they encounter Kin Kwan Cafe’s pretty owner Hui Chin-ying. The duo are certain this is a chance to make career progress as they also find out Yuen Ying Society boss Master Kam is a regular Kin Kwan customer. Hon-sam suspects Mrs Wan has killed her daughter. However, Hon-sam and Sam-yuen have different opinions about whether Ching-ching is still alive. Meanwhile, Mr Wan receives a “letter” from his missing daughter.