So, "420" (1998) is a Hindi drama film directed by Mansoor Khan and written by Aamir Khan, who also plays the lead role. The story revolves around a school teacher named Boman Irani, who gets accused of fraud. The film's title comes from the Indian Penal Code section 420, which deals with cheating and fraud. Aamir Khan's character, Nirmal Bose, is a student who comes to expose the fraud. The film is a classic example of social commentary on educational corruption and the legal system in India.