Chung Lap-Man (Ron Ng) and Lee Pak-Kiu (Sammul Chan) patrolling the streets of Hong Kong with fellow senior constables. During one patrolling shift, Pak Kiu messes with the wrong group of gangs, Cheng Chi-Keung (Wai Ka Hung) and Cheung King-Fung (Michael Tao).
After realizing that Pak-Kiu was manipulated by Chi-Keung, Fiona Ma Oi-Lam (Fiona Sit) tries to clear Pak-Kiu's name from the complaint by Chi Keung. Fiona and Lap-Man finds Chi-Keung and King-Fung dealing drugs in a parking lot and tries to photograph their drugs-transaction. Fiona accidentally sets off a car alarm and is discovered by Chi-Keung and King-Fung, holding her hostage. Pak-Kiu tries to rescue Fiona, instead he gets shot in the side of his head by Chi-Keung and subsequently Chi-Keung shoots Fiona in the stomach, consequently she dies. Pak Kiu then wakes up in the hospital and finds out that Fiona is dead and blames it all on Lap-Man. Throughout the whole series, conflict and extreme hatred for each other is constantly shown between them.
Half a year later, Lap-Man and Pak-Kiu are introduced to their new sergeant, King-Fung. Turns out King Fung was an undercover police officer responsible for the arrest of Chi-Keung earlier. Lap-Man and Pak-Kiu both develop a sense of hatred towards King-Fung. Lap Man gets angry and files a fake complaint letter on King Fung. King Fung's sister, Cheung Nim-Yan (Joey Yung), who is an investigation constable, discover the fake letter prank.
Lap-Man and Pak-Kiu then meets Kuk Ming-Cheung (Chin Ka Lok), who tells him about Pak-Kiu's father, Lee Man-Shing, (Michael Miu). Apparently Pak Kiu's father and King Fung had a bitter past. During this time, Pak Kiu tries to take some psychology classes to try to build up a better resume when he applies for an inspector position within the police department. Yuen Wai-Nei (Sonija Kwok) joins Pak Kiu's classes as she thinks its beneficial to police officers.
Man Ching (Kate Tsui) comes to Hong Kong from the United States in hopes of finding her mother, who turned out to be Lap Man's aunt. Man Ching then develop feelings for Lap-Man, even though she is aware of his girlfriend. Trying to get Man Ching off of his back, Lap Man challenges her to be a police officer at the Police Training School (PTS). Man Ching accepts the challenge. Yuen Ka-Fu (Kenny Kwan), Yuen Wai-Nei's brother, coincidentally just came to Hong Kong from Canada. He was expelled from a Canadian university, and applies to be a police officer. He meets Man Ching in the training.
King-Fung, Ming-Cheung, and a few other sergeants receive a letter that tells them they will be training for the Police Tactical Unit (PTU). During the time at the training camp, Ming-Cheung tries to screw King-Fung over. During the training Pak-Kiu and Lap-Man always get into arguments, their behaviour then noticed by King-Fung, Ming-Cheung. One day Lap-Man tells Ming-Cheung that King-Fung no longer holds a grudge against Man-Shing and that everything is back to normal, Ming-Cheung then becomes all friendly to King-Fung.
At this time, Wai-Nei is still angry over the fact that her ex-husband, King-Fung had "slept" with another woman and that she doesn't forgive him. One day King Fung goes to make this glass vase as it has sentimental value to both him and Wai Nei, he gives it to her and they are back together.
Lap-Man and Nim-Yan slowly starts to get closer and develop feelings for each other. But knowing that Lap Man has a girlfriend, Ho Fa (Tavia Yeung) and Man Ching has a crush on him, Nim Yan backs off. Wai Nei and King Fung's relationship grows and plans to get married. At this time, King Fung encounters Yip Ling-Fung (Selena Li). Ling-Fung runs into some financial problems and King-Fung helps her. On the day of Wai-Nei and King-Fung's wedding, Ling-Fung tries to draw King-Fung's attention by attempting to commit suicide. King-Fung tries to get Ling-Fung to cooperate, but she ignores him, eventually King-Fung has to go with her to the hospital and becomes extremely late for his wedding. As soon as he gets to his wedding, Wai-Nei calls off the wedding and vows that she will no longer be friends or anything with King-Fung. At this time Wai-Nei finds out that she is pregnant with King-Fung's baby.
Wai-Nei soon discovers that Pak-Kiu has developed feelings for her and is willing to be the baby's father. But yet, Pak-Kiu constantly gets nightmares of Fiona getting killed by Chi-Keung. He seeks help from a pschologist which tells him that he actually still loves and misses Fiona. Pak-Kiu is also clear that Wai-Nei still has feelings for King-Fung.
King-Fung, who is unaware Wai-Nei is carrying his baby, heard from his grandmother than Wai-Nei wants to piece back the broken glass vase. He decides to make a new one for her. Wai-Nei receives the glass vase and decides to reconcile with King-Fung. She heads to find King-Fung in Ling-Fung's home, but ends up being held hostage by Chi-Keung.
Wai-Nei ends up hospitalised and severely injured, and Chi-Keung heads to the hospital to deal with King-Fung. Chi-Keung escapes injured, but was caught and shot by Ka-Fu who revenged his sister. Later on, Wai-Nei's condition suffers complications and she is forced to deliver her baby only after a 5 month gestation period.
After delivering her baby, Wai-Nei wakes up and sees King-Fung asleep by her bed. Yet she passed away later on, leaving King-Fung and her family members heartbroken. For the sake of Wai-Nei, King-Fung decides to lead life happily and take good care of their son, Kai-On.
