Au Yeung Wai Yip is a private detective who has been focusing on missing persons and adultery investigations for many years. One day, he received a "special" commission: the owner of the travel agency had asked him to investigate his girlfriend, who happened to be Au Yeung Wai Yip’s wife.

Being a private detective, he is used to looking for the truth with cold eyes for his clients, but he finds it difficult to face the truth about their own marriage. Unable to withstand his inner torment, Au Yeung Wai Yip gave up on another ongoing case - a client's search for his missing fiancée - and went to the hotel to catch the adulterer. Unfortunately, the marriage could not be saved in the end, and the client's fiancée was killed after he left. A seemingly ordinary affair turned into a murderous incident! The police officer in charge of investigating this murder case, Chan Heong Meng, who is seemingly a good policeman and husband, discovers that more than one woman has been killed in a similar manner— the perpetrator is very likely a serial killer.

After handing over the clues to Chan Heong Meng, Au Yeung Wai Yip found himself unknowingly entangled in an intricate web of mystery, with danger looming through the thick fog. To prevent the killer from striking the next target, he must rely on his professional detective instincts to turn the tide.