Against a backdrop of the Republic of China era, fraudster Master Kwan is good at disguising himself as a Taoist priest. He flees to Five Races Town as he gets into trouble. Meanwhile, Kwan’s shenanigans – on the pretext of something to do with god Lu Dong-bin – have alarmed Great Master Luzu, who decides to go to the mortal realm to punish him. Through force of circumstance, Dong-bin is stranded in the mortal realm as he loses his mystical power. And then Dong-bin adopts Lui Shek as his new name while keeping Kwan company so as to help him get back on the straight and narrow. During the process, they solve bewildering cases in the village. A mortal and an immortal run into a prostitute called Pak Suet-fa, and they get entangled. Headman Sun Fu steps down. Kwan covertly prevents bully Kam Shi-ho from standing for election. Newly elected Headman Sun Ching-yee implements reforms as he deals with bad deeds committed by Shi-ho. A series of calamities is triggered in Five Races Town.
Policewoman Yiu Chi-yue is a natural born Highly Sensitive Person. She brings chocolate, salty lemon water and a brain with an “on-off switch” with her whenever she investigates cases. Her senses are heightened when she drinks salty lemon water that arouses her keen awareness of clues at the crime scene. Through touching the dead body, gathering evidence and her senses, she empathizes with the victim and reconstructs the sequence of events. Since Chi-yue met restaurant boss Wong Mik-kei, the duo are no longer “spectators”. Perpetrators at large are killed one after another. Chi-yue covertly challenges some serial killer on several occasions, and their true identity is gradually uncovered. Chi-yue realizes the two of them have conflicting standpoints even though they are like-minded, causing her to face the conundrum of making life choices. In the meantime, Mik-hei astonishingly makes some decision for her.
Sergeant Ko Fai completed undercover operations many years ago, and there is always a cloud hanging over him. Ko Fai is reassigned to a police precinct that is Crime Squad Station Sergeant Fong Chi-kiu’s territory. While investigating cases, the duo gradually familiarize with each other and develop tacit understanding. Chi-kiu is so dedicated to her job that she has no time for taking care of her family. Her son hangs out with the wrong crowd and gets into trouble. Hotpot restaurant lady boss Lo Sin-man was naive when she was young as she slept with gang boss Law Wai and gave birth to a girl called Lo Siu-po. Fortunately, Ko Fai has always taken care of Sin-man and her daughter. Siu-po becomes a KOL and wants to step into the spotlight by engaging in reckless maneuvers. She gradually descends into the abyss as she reveals how drug dealers go about their business. To protect their loved ones, Ko Fai and Chi-kiu become guardians of the night and are determined to eradicate the villains!