•
Louis Koo as Hank Chan (陳克), a former lawyer who becomes a chief investigator of
Independent Commission Against Corruption of Hong Kong (ICAC) after being recruited by his old classmate and friend Nash Pak. •
Tony Leung Ka-fai as
Crippled Ho (跛豪), Hong Kong's number one drug lord. •
Francis Ng as
Chui Lok (徐樂), the corrupt Chief Chinese Detective of the Royal Hong Kong Police Force. •
Gordon Lam as Nash Pak (白松安), chief inspector of the ICAC and Chan's old classmate and friend who recruited the latter to join the organization. •
Philip Keung as Elon (依勞七), a gambling-addicted police officer who was dismissed and beaten by Chui and was recruited by Chan and Pak to join the ICAC. •
Michelle Hu as Yanni Chui (崔瑩恩), Chan's fiance who is a journalist. •
Kent Cheng as Pudgy (豬油仔), Chui's right-hand man. • Jacky Cai as Sharon Lam (林善怡), an ICAC investigator. •
Lam Tsz-sin as Timmy Hui (許大天), Pudgy's former underling who becomes an ICAC investigator. • Mimi Kung as Pudgy's wife. •
Wilfred Lau as Wil (細威), Ho's top henchman. • Dominic Ho as Ron Ho (何國勇), an ICAC investigator. •
Raymond Wong as Ho Ching (何正), Chan and Pak's old friend who is a marine police officer. • Eric Li as Wayne (大威), Ho's top henchman and Wil's older brother. • Parkman Wong as Jan Tse (謝淦生), a corrupt police officer and Chui's underling who was caught red-handed with cocaine shipments and was persuaded by Chan to testify against Chui. •
Wan Yeung-ming as Comic (公仔強), a
triad leader who is Ho's friend. • Chang Yuci as Leia Yung (容海麗), an ICAC investigator. • Ricky Wong as Jackson (強雄), a rival triad leader of Hon who was stabbed by Wil and arrested by the police. •
Derek Kok as Victor (花仔榮), a drug dealer whom Chui plans to groom to take Ho's position. • Yu Kang as Joker (潮州祝), Ho's underling. • Michael Joseph Rosenthal as
Sir Jack Cater (姬達) • Vincent Matile as
Peter Godber (葛柏) ==Production==