Season 1

The series starts off with the head of Team Epsilon assassinated during a police operation. DSP Glenn Chua is then brought in to be the new head of Epsilon. The first season is about the problems and challenges Team Epsilon faces as they try to bring down an illegal syndicate called "Angel", which is based in Thailand. Near the end of the season, it was revealed that Glenn's best friend, Jackson (Jourdan Lee) is actually the son of the head of "Angel" and he is then shot by Vivian (Pamelyn Chee) in the season finale, after threatening to kill Glenn.

Season 2

Season 2 focuses more on the problems faced by the Singapore immigration and checkpoints and also on Glenn's dilemma after losing his best friend, Jackson. It also reveals that Vivian and Jackson had a son named Jonah. As the season is more about problems in Singapore, it features less of the "Angel" syndicate in Thailand. Noi, Jackson's sister got married but soon finds out that her husband murdered her father in an attempt to take over "Angel" syndicate. Her father's death caused her to lose sanity and she killed her husband. Nearing the end of the season, Vivian is killed by Noi, after being locked up in a burning abandoned warehouse. It was to gain possession of Jonah who is her nephew and also to avenge Jackson whom Vivian killed. But Glenn would not let Noi take Jonah away and he becomes Jonah's guardian. In the season finale, it was revealed that Jackson is still alive and the season ends with a cliffhanger of Glenn assassinated by Jackson.

Season 3

Glenn Chua survived the attempted assassination by Jackson and took a long leave from Team Epsilon to take care of Jonah. Jackson disguises himself as Virote Boonprasong and continue his illegal dealings in Singapore. He had become the new head of "Angel" syndicate and strives to bring the syndicate back to its former glory. He frequently visited his sister, Noi, in prison to make plan for her escape. Glenn managed to see through Jackson's disguise and begin work his way to find proof. Jackson wanted his son, Jonah, back and began to make plans. In the end, Jonah was kidnapped by one of Jackson's associates in the Philippines, Miguel. The season ends with Jonah saved and brought back to Singapore by Cheong, while Glenn and Jackson faced off in a final fight which resulted in Jackson being killed by Glenn and ending off with a cliffhanger of Miguel aiming his gun at Glenn.

Season 4

Glenn Chua is on the run. Glenn is a wanted man in Philippines for killing Jackson and framed for killing Miguel. He joins an illegal Filipino syndicate, "Multo", in order to survive being hunted by the police. "Multo" specializes in making a new set of dangerous drugs, named "Helo Yelo". Later in the series, Glenn returns to Team Epsilon.

New threats and villains appear in this season, as Team Epsilon takes on a new international syndicate based in the Philippines that will not stop at any means to perpetuate their heinous activities: human trafficking and drug smuggling.

Leader Glenn Chua (Jack Yang) goes deep undercover to sift out the complex web of players in this organisation and bring down its hidden mastermind, while veteran Cheong Guan Meng takes over the reins during Glenn's absence to lead the members: Tech expert Norah Rahmat, parkour expert Dynesh Krishnan, gung ho valiant Matthew Yong, with the support of their boss Calvin Wong and Home Team liaison Kara Yeo. New member, ASP Sophie Thomas (Liv Lo), from the CID Anti-Vice department joins the team, and CID Intel Officer Victor de Cruz takes over guardianship of his nephew, Jonah. Multo's new head, Analyn Ocampo (Padilla Bela) gets close to Glenn Chua, to the extent of marriage, but for an ulterior motive, as to move "Multo" into Singapore's line of underhand illegal activities.

Near the end of the series, Analyn gets unmasked as the head of "Multo". She would be eventually arrested in Philippines, halfway through her wedding, and unexpectedly by her husband-to-be, Glenn Chua and Kara Yeo. Sophie and Dynesh would get together, along with Glenn and Kara (Presumably).

Team Epsilon

Other cast