Chen Junhao (Christopher Lee) is a righteous and courageous police officer who graduated with top honours from Old Police Academy and harbours the ambition to follow his father Chen Rongyao's (Moses Lim) footsteps into the elite Criminal Investigation Department. He is sorely disappointed when he learns that he has been assigned to a neighbourhood police centre. At the NPC, Junhao and his colleague Wang Feng (Allan Wu) do not see eye to eye and their relationship further deteriorates when Junhao accidentally mistakes Wang Feng's father Wang Jiancheng (Huang Wenyong) for a burglar and "arrests" him because he was merely asking his wife Zhong Xiaolan (Lin Meijiao) for money but she refused to give him money anymore because he was extremely addicted to gambling and owed lots of money to multiple loan sharks. As a result, to no avail, he went on to attempt housebreaking and stole money at the Wang family's home, which they lived in a Ang Mo KioHDBFlat located at Blk 170, Ang Mo Kio Avenue 4.
During a big fire, Junhao saves the life of an old lady (Li Yinzhu), earning the adoration of the old lady's granddaughter, Irene (Yvonne Lim), who is the neighbourhood "ah lian". Much to Junhao's annoyance, Irene tries to come between him and his colleague-cum-love-interest, Cai Kexin (Phyllis Quek).
Wang Feng falls for Junhao's younger sister Chen Huimin (Jeanette Aw), a Nurse working at Singapore General Hospital and attempts to patch up his relationship with his younger brother Wang Wei (Zen Chong). He eventually changes his mind about Junhao when the latter saves him during a mission. Junhao also accepts Wang Feng after uncovering his troubled and complex family life.
Junhao's best friend Wu Zhiguang (Cavin Soh) uses his identity to commit multiple sex crimes and Junhao ends up taking the rap and is jailed. Kexin's younger sister Cai Kejuan (Zhang Chunmei) has been kidnapped by Irene as revenge against her for causing the latter's grandmother's death in a traffic accident. Wang Feng witnesses the stabbing of Wang Wei, who eventually dies in the hands of a Loan Shark named Hui Ge (Ye Shipin), whom is an enemy of Jiancheng and wanted to take revenge on both him and his younger son Wang Wei. Each officer is tested as their jobs soon catch up with their personal lives.
