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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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, risking revealing his real identity.
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.
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.
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.
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.
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.
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.
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.