Aan is a movie about a bunch of policemen and their complacency towards their job. DCP Hari is posted to a Mumbai police station only to find out that his entire team has completely forgotten the rules, regulations and duties to which they swore when joining the police force. However, he loses his temper when a man from his team is killed by a man he himself released from prison. He swears to clean the city which is under the command of three officers and hence, starts a series of encounters. It is about the consequence of such an approach and its reciprocations.