It is the early 1980s, and Singapore is a young nation on the rise. Joyce Goh arrives in Singapore from the USA, to bring her late mother's ashes back home to rest. 20-year-old Police Constable Patricia Yeo has a chance to work on an exciting case when an alleged rape is reported to her Neighbourhood Police Post. Kiat, Seng Hock's son, seems to have fallen in with some teen gangsters. Will he follow in his father's footsteps ...

The CID is in a race against time to find a serial killer before he commits yet another brutal murder. Kiat gets further drawn into the illegal activities of a teen gang and fears for the safety of a more impressionable classmate. Joyce is faced with a choice: will she stay in Singapore and join the police force like her mother did?

A few years have passed. Patricia is now in the CID and Joyce has also been recently transferred there. The CID team, under the leadership of now ASP Tan Han Lim, investigates a teen gang assault. Patricia and Joyce learn to cooperate, despite different working styles, and both are asked to audition to be the new host of Crimewatch. Kiat, working undercover, gets a new job at a video shop owned by Dennis' gang, hoping to work his way up ...

The team investigates a mysterious case of murder and arson. Kiat tries to find out more about the gang's illegal activities but finds himself frustrated by fellow gangster Gary, who tries to keep Kiat under his thumb. Joyce collects a box of old things from her late grandmother's home, and makes an interesting discovery about her mother's past.

Patricia and Han Lim, with their common interest in local cuisine, start to have more meals together, and are spotted by the other CID officers, who start to gossip. Joyce gets one step closer to finding out exactly who "Hock" was to her mother Elizabeth, and the team investigates a possible hostage situation in a wealthy neighbourhood.

Tommy, Patricia's ex-boyfriend and a former member of Dennis' gang, is released from prison. While he hopes to turn over a new leaf, he finds it difficult to distance himself from the gang to which he once belonged. Joyce struggles to connect with her sister Emily, who rebels even more when Joyce refuses to trust her. Meanwhile, the CID team investigates a murder at a private condo and uncovers secrets, lies and manipulations within the ...

The team investigates a robbery-gone-wrong that results in the death of an elderly landlady. Kiat and Joyce discover that their late parents had known each other in the past and continue exchanging letters. Patricia and Han Lim are the subject of office gossip, causing Han Lim to change his behaviour towards her. Meanwhile, Tommy has taken over as the boss in the gang-run video rental shop, and Kiat manages to impress him with his initiative ...

The team investigates a macabre case of a murder victim cooked in a pot of curry. Tommy is put in charge of the gang for the time being, while Eric and Dennis seek out new business opportunities overseas. Emily gets herself into trouble yet again, this time with potentially disastrous consequences.

Kiat continues to impress his superiors, and is assigned greater responsibilities in his gang. Patricia and Joyce become better friends after Patricia helps Joyce to save Emily from a spot of trouble. Tommy reconnects with Patricia and he convinces her that he's turned his life around. The team investigates an upsetting case – the disappearance and eventual murder of three young children.

A serial rapist terrorises teenage girls in the eastern part of Singapore, and the CID team has to find him before he strikes again. Joyce is pleased when her usually irresponsible sister Emily gets a part-time job at a video rental shop, but she is less than impressed by Emily's new colleague, Kenny, whom she thinks is a shady character. Tommy and Patricia make up for lost time and rekindle their past romance.

The CID team investigate another murder when the dead body of a rich man washes up on the shore one day. Kiat discovers new illegal dealings that the gang is involved in and tries to probe further, at the risk of his real identity being uncovered. Joyce worries about her sister Emily working with Kenny, and confides in her pen-pal Kiat.

The CID team uncovers the motives for what appears to be a crime of passion, while undercover Kiat finds out that Eric and his gang have ambitions to move into the drug business. Patricia and Tommy grow closer and Patricia tells him about a painful incident in her past, unaware of Tommy's role in it, and of his current gang connections. Just as the relationship between Joyce and her sister Emily start to improve, Joyce receives news from ...

A series of brazen armed robberies in broad daylight sets the CID team on an exciting manhunt and chase. Kiat has gained Tommy's trust and finally gets to meet the gang boss, Eric, in person. Joyce and Kiat's friendship deepens through their correspondence and they share a close connection. However, Joyce is hurt and disappointed when she eventually finds out who her pen-pal Kiat really is. Meanwhile, Dennis uncovers a secret ...

A decomposing body is found in an old fishing village and the CID team has to solve the mystery. Disappointed that her pen-pal Kiat had been lying to her, Joyce stops writing to him. Kiat gets closer to Eric and his gang and leans more about their big plans to smuggle drugs into the country. Dennis tells Eric the secret that Tommy has been hiding. Furious that Tommy has lied to him all these years, Eric orders Dennis to kill them both ...

The CID team tracks down a gunman responsible for the execution of a provision shop owner. Kiat makes the painful decision to write Joyce a final goodbye letter. Patricia is confused by Tommy's sudden disappearance, and begins to question everything she knows about him, unaware that her own life is in danger. Meanwhile, ASP Lee Boon Ping from the Intel Division finds out from Kiat that Patricia is dating a known gangster, Tommy ...

A shocking discovery of dismembered body parts leads the CID on an investigation to find the savage killer who's responsible. Patricia is unhappy at being questioned by Intel regarding her relationship with Tommy. Will she reveal to the police that Tommy has made contact with her? Gary is released from prison, and is eager to start working for the gang again, but this time, he faces Kiat as his rival for Eric's approval. A disgruntled Gary ...

Anand is still worried about Han Lim due to his recent health scare, but Han Lim dismisses his concerns and leads the team on a new investigation into the violent assault of two Japanese tourists at East View Hotel. Gang boss Eric seems to be distracted by yet another business venture – the opening of a new nightclub. Kiat suspects that something bigger is brewing… Patricia feels deeply conflicted about her feelings towards Tommy. When he ...

Joyce finally learns the whole truth about Kiat's undercover work, after he ends up in hospital in a serious condition. The CID is out in full force hunting down both Eric and Tommy. Patricia is disillusioned by what she feels is the team's lack of trust in her, and finally makes her decision. Before she can act on it, she is abducted. The police finally catch up with Eric and Tommy in a tense showdown. In the wake of their successful man...