A police officer receives a worn-out and traumatised woman who begs him to take actions against a ruthless man that ruined her life, and only gives his moniker, Tín Mã Nàm, meaning “crazy horse” in Cantonese. As the officer sets out to search for Tín Mã Nàm, a network of intricate crimes, espionage and bloody murders beyond his imagination begins to unfold.