Gu Yi, a detective from the underworld, refused to be reincarnated after dying in the line of duty and chose to be a criminal policeman in the underworld. With the purple flame that burns away sins in his left hand and the black flame that devours souls in his right hand, he walks between the Yin and Yang realms, specializing in solving the horrific and mysterious cases in ancient and modern times that have been sealed in time and avoided by ghosts and gods.
