In 1955, Gerard and Annie Wee are murdered in cold blood by unknown assailants. They are survived by two daughters, whose fates take a different path from that moment on. Seng Hock is asked by the police to betray his Ang Huay brothers. Johnnie Goh returns, determined to make Elizabeth fall in love with him, but this could not have come at a worse time.

As Sadeeq and Hani consider an attractive job offer overseas, Elizabeth and Yoke Lien receive some terrible news. A group of vengeful gangsters are out to exact revenge on Seng Hock. The team looks into the case of a woman's missing husband, and Elizabeth makes a difficult decision.

It's the first day at work for inspectors Margaret and Shanti, who have just joined the Organised Crime Branch of the CID, but Margaret's enthusiasm gets the better of her. A pair of young gangsters, Roy and Tony, both eager to prove their worth, start to make waves in the underworld. The body of a young girl is found in a well, and the team works with Dr. Peter Beh, forensic pathologist, to solve the case.

Margaret finds a photo of a house in an old case file familiar, but doesn't know why. Sadeeq broaches the idea of having another child with Hani, but she hesitates, wanting to focus more on her career. A jaga kereta boy is found dead after getting into a fight with a driver over "parking fees", but the driver insists he's not the killer.

As the team deals with the scourge of illegal blue film distribution in Singapore, Margaret continues to be baffled why the Wee family house, site of the Wee Murders of 1955, feels strangely familiar to her? Hani struggles with prioritizing her family over her career, and Shanti considers pursuing studies in law.

Margaret is overjoyed at the return of a childhood friend, and Shanti faces off with Charles over his chauvinistic tendencies. A Japanese woman is found stabbed in her own home, and Margaret goes undercover in a nightclub as part of the investigations. However, this only leads to more questions, as Margaret makes a shocking discovery.

Dr Peter Beh and Margaret build up a rapport that unsettles her childhood crush, Alan. Cabaret girl Helen is faced with a difficult choice between marriage and vengeance. Three bank robbers execute a daring bank heist in broad daylight and spark off an island-wide manhunt.

Margaret discovers that her mother, Ah Ying, has been secretly corresponding with someone for many years. A multi-millionaire makes a narrow escape from his kidnappers but they refuse to give up so easily. In order to catch the kidnappers, Boon Ping is assigned to stay in the rich man's home and pose as his cousin.

Margaret and Helen look for Nancy Ang in Gemas but they are not alone in their search. Meanwhile, the team is on high alert after more than 30 inmates break out of a Bedok reformative centre, one of whom is a hardened criminal who goes out on a crime spree.

Seng Hock comforts Helen and she makes a surprising move in the heat of the moment. Margaret is visited by an unexpected guest in Singapore and Helen is struck by a shocking revelation that brings her closer to the truth she's been seeking all these years. Meanwhile, a gang is harassing doctors (one of whom is Peter's friend) in the Thomson area for protection money.

Helen's happiness is short-lived as her recent discoveries come to an abrupt dead end. Boon Ping investigates a series of car thefts in his neighbourhood but suffers an unforeseen setback when he gets suspended for corruption. Meanwhile, Hani and Sadeeq eagerly await a wonderful arrival to their family.

The team investigates the cold-blooded killing of one of their own. Helen involves Margaret in a rash decision that might just put Margaret's career on the line. Meanwhile, Tony helps Helen fend off a troublemaking customer at the nightclub, but do his actions do more harm than good?

Margaret stumbles upon a surprising new piece of evidence in the Wee Murders case. The team attempts to uncover the mystery behind the seemingly random stabbing of a wealthy woman. Roy and Tony commit a serious act that could jeopardise their future with the gang.

Margaret tracks down former Inspector Kong to talk to him about the Wee Murders case. A distinctive gun is used to commit a robbery at a goldsmith's and the team uncovers a gun-rental business. Roy and Tony resort to drastic action under pressure, and Seng Hock offers to help them.

Faced with new discoveries, Margaret is determined to arrest the mastermind behind the Wee Murders and she ropes in the help of others. Shanti finds herself in a dilemma between love and her career while deciding whether or not to pursue her dream of becoming a lawyer. Meanwhile, when a young woman is found dead in a deserted spot, her boyfriend and a married man are both under investigation.

Three years have passed; Margaret has been promoted to the rank of ASP and Shanti has just returned from her law studies in London. Shanti's cousin has a personal crisis and she seeks Shanti's help. Seng Hock, now a more senior member of Tong Hup, faces the results of his actions in the past. And Charles, who has been transferred to the newly formed Central Narcotics Bureau, investigates an international drugs smuggling gang with surprising ...

The team investigates the murder of an unidentifiable Caucasian man as they attempt to stall the efforts of a notorious drug syndicate that threatens to use Singapore as a means to further their empire. Seng Hock gets an unexpected visit from an old friend, and Margaret starts to become suspicious of someone close to her.

The heartbreaking murder of four young children is one of the most horrendous crimes the CID and Dr Peter Beh have seen in all their years. The leader of a notorious drug syndicate based in Amsterdam is due to arrive in Singapore, and the police prepare to make a big arrest and bring down the key members of the syndicate. Margaret's suspicions lead to shocking discoveries for her, both personally and professionally.