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 a triad, and a police officer secretly working for the same gang. The Chinese title means "The Unceasing Path", a reference to Avici, the lowest level of hell in Buddhism, where one endures suffering incessantly. The English title is a word play combining the law enforcement term "internal affairs" with the adjective "infernal". Infernal Affairs was followed by Infernal Affairs II and Infernal Affairs III.