Lee Pak Kiu and Chung Lap Man, buddies since they were both in the Police academy, are now living together. Pak Kiu is a very neat and tidy person while Lap Man is messy and disorganised. Pak Kiu is now attached to the Emergency Unit, while Lap Man is with the Vices Department.
One day while following a drug suspect, Lap Man managed to spy on some people manufacturing powder. He suspects that they are producing drugs and quickly request for back up from NB (Narcotics Bureau). However, the powder is actually flour and the people are making fishballs. However, they are operating without license. Lap Man was scolded by his superior.
Kong Sai Hau was released from prison in Taiwan and Chung Hing's (a triad society in HK) leader, To Lek Tin went to pick him up. Tin Ko wants to set up a business for Hau Ko to run in Taiwan but Hau Ko declined. Hau Ko wants to return to Hong Kong to be reunited with his daughter, Yau Yau.
Back in Hong Kong, Tin Ko invited Hau Ko to stay with him and his wife, Sam Jie. Sam Jie also offers to help Hau Ko to look for his long lost daughter.
Hau Ko's return to Hong Kong c=managed to create some discomfort amongst the triad leaders. Tin Ko throws a welcome dinner for Hau Ko, but during the dinner, Laughin Ko (a leader of the triad) creates some problems for Hau Ko. Laughin thinks that Hau does not deserve to be one of the new leaders of the triads but the triad seniors thinks Hau Ko deserves it as he was incarcerated because of Tin Ko. Laughin also find chances to frame Hau Ko for possession of drugs. He then reports to the police. Pak Kiu arrived to check on the situation and is shocked to see Hau Ko, who is the splitting image of his dead father, Lee Sir.
Pak Kiu could no longer bear with Lap Man's untidy surroundings and hired a housekeeper, Fa Si Lai.
Pak Kiu arrests Hau Ko as he possesses drugs. Hau Ko was interrogated by the police but insists that the pills were not his. Chun Hing sends a lawyer over to post bail for Hau Ko.
Lap Man notices that Pak Kiu is sad so the two of them goes fishing. But, they ran into Hau Ko at the fishing place and Lap Man takes the opportunity to know Hau Ko better. The there of them went for dinner together. Hau Ko shares some stories of his past with them.
Pak Kiu's superior receives news that he had dinner with Hau Ko and advices him not to get too close to people from the triads. On his rounds, Pak Kiu bumps into Hau Ko, Tin Ko and Laughin Ko. Tin Ko's car was illegally parked so he issued a summon for Tin Ko. During the car ride, Laughin Ko told Tin Ko that he doesn't have much money and expressed his interest to dabble in drugs. Tin Ko agrees to Laughin's request.
Sam Jie receives payment from Yau Yau and informs Hau Ko. Sam Jie receive news that there are a few new Taiwanese girls working at a nightclub and goes with Hau Ko to see if Yau Yau is among them. Hau Ko is upset with Sam Jie as he thinks Yau Yau will not venture into prostitution. Sam Jie felt offended as she was once a prostitute and walks away from Hau Ko. Yau Yau calls Sam Jie to tell her about the money and Sam Jie asks her where does the money come from. Yau Yau tells Sam Jie that she sells pirated DVD.
Lap Man bumps into Yau Yau selling DVD. He also finds out that Yau Yau has a blog called "Little Princess" and she is his informant's (La Ba) housemate.
Laughin Ko finally gets the chance to deliver drugs. He assigns the task to one of his debtors but his debtor gets his young (around 10 to 12 years old) son to do it. Hau Ko heard the story and does not want the little boy to end up like Yau Yau so he snatches the little boy's backpack (which contains drugs). Lap Man was trailing the boy when he saw someone snatches the boy's bag and gave chase. Lap Man request for back up and Pak Kiu's team was nearby so they gave chase. However, when he finally caught up with Hau Ko and Laughin KO, they could not find any drugs.
Actually Hau Ko stashed the drugs somewhere and went to collect it later. He doesn't want the little boy to end up like Yau Yau (i.e. 10 years ago, he and Yau Yau helped Tin Ko to carry some goods which he didn't know were drugs. When he went to buy a drink for Yau Yau. the policemen found Yau Yau carrying drugs. They took her away and Hau was imprisoned.) Hau Ko was beaten up by Laughin Ko because Hau Ko told Laughin Ko that he threw away the drugs. Sam Jie wanted to send Hau Ko to the hospital but instead Hau Ko brought her to retrieve the drugs.
Sam Jie knows that Hau Ko has sacrificed a lot for Tin Ko. She takes the opportunity to put in a few good words for Hau Ko when going out for morning walk with the tried elder. Tin Ko and the two triad elder decided to award Laughin Ko's mega disco business to Hau Ko. Laughin Ko is upset and disagrees with the triad elders' decision but he unable to change it.
Lap Man knows that Yau Yau copies the content of a comic series for her blog. He visits her blog anonymously and exposes her.
Lap Man's superior assigns him a task - to close down illegal gambling stalls by the sidewalk. While on duty, he met Yau Yau selling pirated DVDs. Coincidentally , the customs were making rounds and Yau Yau quickly packed up to flee. She asks Lap Man for help and pass one bag of DVDs to him, which he conveniently handed them over to the customs. Lap Man later reveal to Yau Yau that he is a policeman.
Yau Yau spotted Sam Jie together with Hau Ko going around looking for her. She warns Sam Jie not to look for her anymore or else she will leave Hong Kong.
Lap Man continues to investigate the illegal gambling case and runs into Yau Yau. Yau Yau demands compensation from Lap Man for the DVDs that he gave to the customs officials. As Lap Man is on duty, he gave Yau Yau HKD 1000 to shut her up and make her leave. But Yau Yau intentionally reveals Lap Man's identity and which makes the illegal gamblers flee immediately.
Pak Kiu and his team were making their rounds when they saw a group of teens high on ecstacy. One of them, a girl was standing on the edge of a very tall building. Pak Kiu tried to save the girl but she let go of Pak Kiu's hands and fell off the building. Pak Kiu was upset by the incident.
Pak Kiu was suppose to give a speech to students about the dangers of drugs but he could not do it after the incident. However, his superior encouraged and advised him to continue with what he has started> Pak Kiu managed to give a very touching and emotional speech.