In this good cop versus bad cop action thriller, Detective Chan (Simon Yam) relentlessly pursues crime boss Po (Samo Hung) but eventually gives up in frustration and looks toward retirement. His replacement, Ma (Donnie Yen) is a principled, committed cop who is skilled in the martial arts and has a reputation for violence. The newcomer introdfuces tension the established ranks of the battle-scarred precinct. The death of a cop who was planted undercover in Po's gang further disrupts the balance of truth and justice.
SPL refers to 3 stars in the chinese astrology that symbolize that dangerous characteristics of Chan, Po and Ma. These 3 stars, with their changes, could create or destroy the beautiful life of each other.