Fai Yan and his younger sworn sister Ko Keung become Lo Yan County Yamen constables. Newly appointed Head Captain Wong Se tells Fai Yan to go to anarchic Yat Tseung Kung City to look for some spy who has lost contact. Boon Lung Sect boss Boon Dau’s minion Moyung Gong-tsz accidentally takes Fai Yan to Yat Tseung Kung City. The city is seemingly a prosperous place, but the four major sects are covertly fighting against each other. The late sect leader promised whoever could draw the Infernal Sword, Tsui Yi Sect Big Sister Fu Ling would marry him. Fai Yan and Gong-tsz confusingly draw the Infernal Sword together, so they both become the top two prospective sons-in-law! The four sects engage in all kinds of shenanigans, and the mastermind has tricks up their sleeve. The identity of the spy is just mysterious. Fai Yan wants to be the prospective son-in-law. And the Yamen spy has to be tracked down. No one knows whether it’s a blessing or a curse.