Feng Nan Tin leads a group of elite constables who investigate strange mysteries from all across the country. His position gives him authority over local magistrates and even the six ministries. Chu Cheung Seng with his combination of bravery and wit, is Feng Nan Tin's favorite subordinate. However, they go their separate ways after disagreeing on a robbery case. Chu Cheung Seng and his wife Yan Mei Neong disappear for nearly ten years. When the case finally comes to an end, the aging FENG NAN TIN orders MA Cyun Giung, Ngau Dai Lik and Yeung Maau to find Chu Cheung Seng and ask him to rejoin the team. Together, the four constables solve many mysteries together, but conflicts often arise due to their different personalities. Chu Cheung Seng and Yan Mei Neong also experience difficulties and separate because of a misunderstanding. When Chu Cheung Seng meets a prostitute who looks exactly like his wife, he feels lost and delirious. Meanwhile, the Jurchens are preparing to attack the Song Dynasty. Chu Cheung Seng discovers that the Jurchens have planted a spy amongst the constables. His good friend, Hung Sap Gau, is unwittingly used by the Jurchens. Others subsequently fall into danger as well. It becomes difficult to distinguish between friend and enemy, leaving everyone feeling insecure.