Former CID detective Sze Tou Shun was forced to leave the police force due to suspicions that he was involved in an arson case. He joins a security company, where he meets Cheng Lik Hang. As a former detective, Sze Tou Shun has a reclusive character, but has a sharp eye that can catch tiny details from surveillance footage which are often the key to solving cases. Cheng Lik Hang's thinking and style of working is similar to Sze Tou Shun's and is also excellent at his job. The two become good friends and are looked upon favourably by their superior. This is until private investigator Ng Zan Nei appears. Conflict arises when she mistakes Sze Tou Shun for an old friend. It causes him to recall a long-forgotten incident, which turns out to be related to the arson case. Ng Zan Nei, known to possess a human "eye in the sky", continues to investigate along with Sze Tou Shun and Cheng Lik Hang, but as they get closer to the truth, the conflict between emotions and the law grow more fierce and the relationship between the three of them experience a big change.