A Prince of the Song Dynasty is going to shave his head and pray for the people. At the tonsure ceremony, the abbot who performs the ritual attempts to assassinate the Prince, but is thwarted by the Field officers of the Phecda Bureau, YEUNG MAU, NGAU TAI-LIK and MA CHUEN-KUNG, in the nick of time. The leader of the Phecda Bureau, FUNG NAM-TIN, leads his troops and tries to enter the ceremony venue, but is hindered. Showing the badge given by the Emperor, NAM-TIN states that the Phecda Bureau is under the Emperor's immediate supervision. Following a prisoner SOU FU's escape, Commander SHE PAK-NIN analyzes the reason and tells NAM-TIN about it.

As SOU FU's case is successfully drawing to a close, CHUEN-KUNG asks CHEUNG-SING to go back to the Phecda Bureau together with them. Upon their return to Bianjing, CHUEN-KUNG spots a bridal sedan passing by, knowing that Minister HO, under the Emperor's decree, is going to marry off his daughter outside of the town. As soon as CHEUNG-SING enters the Phecda Bureau, his childhood best friend, PAK-NIN, hops out to challenge him. Apart from reprimanding CHEUNG-SING for not showing any repentance, NAM-TIN also wants CHEUNG-SING to resume his duty as the Commander, but CHEUNG-SING refuses to do so.

Having gone through an investigation, PAK-NIN deduces that it could be a fallen meteor. However, the fallen meteor is regarded as an omen, NAM-TIN feels very annoyed as he has no idea how to report this to the Emperor. CHEUNG-SING intends to let his wife TAO FA stay in the Phecda Bureau, unexpectedly, NAM-TIN requests TAO FA to move out. Later on, NAM-TIN meets up with TAO FA, handing her a key as well as a title deed and telling her to run the business of Peach Blossom Grove. After Minister YUEN is found dead and dumped outside of the Phecda Bureau, CHEUNG-SING goes to investigate it and learns that the late Minister YUEN often hung out at night.

Someone, who self-claims to have possessed the sulphur, goes to the Phecda Bureau to turn himself in, yet, PAK-NIN believes that he is just a scapegoat. CHEUNG-SING wants to meet HUNG FUNG but is rejected; whereas NAM-TIN also tells him that he has already instructed the Moon Section to look into the case. At the opening day of the Peach Blossom Grove, SAP-KAU delivers lavish gifts when TAO FA is distributing the flyers, and he even promises to stay there and help improve their business. CHEUNG-SING and his three fellow colleagues go to investigate at the Chaoyang Peak, where they uncover a cannon, so CHEUNG-SING suspects that the late Minister YUEN had a secret mission.

Though PAK-NIN claims that it's impossible to search for the suspect CHAN CHIT-WO among the Dragon Gang, CHUEN-KUNG believes those who have been exposed to explosives for a long time must show a variety of abnormal symptoms. Field Officer CHOI follows CHI-SIN and discovers that he has several symptoms which seem to be identical to those, which, according to CHUEN-KUNG, might appear on the body of CHAN CHIT-WO. Prince TUEN surmises that the reason why the Phecda Bureau is able to solve the case is because they stole the log. Nonetheless, the Emperor decides not to blame those of the Phecda Bureau anymore as they have atoned for their errors. Suspecting that CHI-SIN is not the only one involved in the case, CHEUNG-SING and CHUEN-KUNG cannot help worrying about the Emperor's safety, so they dash to the venue where their Emperor and the Jin Emperor sign the treaty.

With the Phecda Bureau finding out that it's KWAN CHIU who made the poison, CHUEN-KUNG and the others go to arrest KWAN CHIU and bring her to justice. KWAN CHIU bears a grudge against the Bureau after she is tortured during the interrogation, so she forces some civilians to swallow the poison. Finally, CHUEN-KUNG knocks her unconscious and sends her out of Bianjing. Constable KWAI-CHEUNG is attacked and suffers severe injuries, lapsing into a coma. He is rescued by PAK-NIN and his team who take him back to the Phecda Bureau. KWAI-CHEUNG turns out to be a spy, who penetrated into the Jin Dynasty and uncovered that there have been Jin moles in the Song Dynasty. Unfortunately, the confidential correspondence with a full log of details has vanished without a trace. CHEUNG-SING encounters his old acquaintance CHAU-YUET, who doesn't recognize him.