Infernal Affairs is a 2002 Hong Kong crime-thriller film directed by Andrew Lau and Alan Mak. It tells the story of a police officer who infiltrates the Triads, and a police officer secretly working for the same gang. The Chinese title means "the non-stop path", a reference to Avici, the lowest level of hell in Buddhism. The English title is a word play combining the law enforcement term 'internal affairs' with the adjective Infernal. Due to its commercial and critical success, Infernal Affairs was followed by a prequel, Infernal Affairs II, and a sequel, Infernal Affairs III, both released in 2003.