Veteran police officer, Bai Qingxiong (Chen Hanwei), forms an agency called Cold Case Investigators (CCI) which aims to crack unsolved cases. Through this agency, he hopes to give a proper closure to family members of the victims. He is a righteous man who is confident that all criminal will not escape the law. The CCI uses unorthodox methods to search for clues which eventually led them to the truth. There are many clashes among the team during the investigation process but sparks also flew among young members, Huang Yuyang (Rebecca Lim), Hong Junyan (Desmond Tan) and Lan Haifeng (Yusuke Fukuchi). The trio soon find themselves entangled in a love triangle. Each time the team manage to solve a case, they are also reminded of their own mystery past. It seems that Qingxiong, Yuyang, and Junyan each have a secret from the past which they are unable to let go of. Eventually, they all decide to work together to investigate their own mystery cases. Can they solve the cases and finally let go of the past?