No. of episode: 37
Genre: Police, Action, Thriller, Undercover, Triad, Investigation
Native Title: 使徒行者3
Original network: TVB
The drama is the third instalment of the Line walker series and focus back on Sit Ka Keung aka Bao Seed (Raymond Lam) on his journey to find the love of his life Ding Siu Ka aka Ah Ding (Charmaine Sheh) who parted ways due to another undercover mission.

Uncovers
Bao Seed set his mind to find the whereabouts of Ah Ding alone. He open up a foot spa parlor that mimic the one that Ah Ding opened years ago. Bao Seed did not join back the police force and people are unaware of his identity.
The release of Cheuk Hoi (Michael Miu) after 3 years of jail time make him call it quits for both black and white side. Cheuk Hoi did go to prison to save Bao Seed three years ago (the finale of Line Walker season 1). However, the friendship he built with different triad bosses made them want to recruit him to their respective gang.
Cassidy aka Ah Dau (Sisley Choi) is an undercover sent to investigate both Bao Seed and Cheuk Hoi by Madam G (Mandy Wong). After their identity is cleared and clean, they are recruited to be undercovers, and all report to Madam G.
Ah Dau fell in love with the triad boss Pong Ho Yeung aka Ah Fo (Owen Cheng) while performing her investigation.
2009
A mystery package was delivered to Chang Suk Mui aka Ah Mui (Priscilla Wong) and it contains digital logbooks of undercovers 10 years ago. Ah Mui was a CIB undercover but now she is a journalist and influencer that goes around to cover stories and crossing the lines.
Ah Mui’s target is Paradise, Chui Tin Tong (Benjamin Yuen) who happens to be her best friend and housemate. Tin Tong went back to the police force after his undercover job is done, but the top management still suspect he is not clean.
Back in 2009, Ah Lun (Shiga Lin) and Wing Cheung (Tony Hung) was sent to investigate Tin Tong as an undercover.
CIB met SIA
Hong Kong’s Criminal Intelligence Bureau better known as CIB started shaking when they met a newly setup agency that aims to go against CIB to seek justices. SIA, the Security Intelligence Agency is a firm outside of the police force and head by Wai Chok Wing (Kenneth Ma).
In a nutshell, there are too many things happening within the 37-episode and it can be pretty confusing for a starter. Advice to watch both the prequel as the cast and storyline is closely knitted.