First, let me make it clear I have seen the Tamil version of the movie.
The movie is about a corrupt mayor (Kamal Haasan) who is killed and cold stored by his allies turned foes. They find a person (Kamal Haasan)who looks similar and a run away mate of a mental assylum, He is made (imposter) Mayor.
The movie is made as Comedy, but it turns vulger at several places (I still remember my blushes - as I was with family - from the scene just before the intermission).
Kamal Haasan is excellent as both the Indran (Indrudu in original) as well as Chandran (Chandrudu in original version).