He will kill you with laughter unless you cry for mercy?In the early 70's ? Bombay was taken over by smugglers and gangsters. One of them was Don Muthuswami (Mithun Chakraborty).
Muthuswami's father is on the deathbed and Muthu comes to see him and pay his last respect. As he comes close to his father, his father slaps Muthu and tells him that he has brought shame to the family by being a gangster and that he would die an unhappy man. The Don asks his father what he could do to bring his father peace in his last moment. He extracts a promise from his son that he would go straight. Thus begins the Drama of Don trying to change into a gentleman.
Muthu tells his henchmen to continue working for him, but now instead of being gangsters they have to work as domestic help. He engages an Urdu/Hindi teacher Jaikishan (Mohit Raina) to improve his language. He starts his journey to transform from Don Muthuswami to Sir Muthuswami.
To this is added the confusion of his daughter Sanjana's (Hrishita Bhatt) marriage. Best match according to him was his very good friend Don Vardhan's son Pradhan to which Sanjana refuses. So she lies that she is pregnant. Muthu's general manager, Preetam (Rohit Roy), who wants to marry Muthu's daughter, is another dimension of this comic confusion. He had been stealing regularly from Muthu, to make himself a millionaire. Then comes, Ranjana (Anusmriti) who tells Muthu that she loves his accountant Preetam. She also admits to Muthu that she had lied to Preetam about being Muthu's daughter.
In the meanwhile, Sanjana and Jaikishan fall in love with each other and make things more complicated. How does Muthu get back the loot from Preetam? Who is the father of Sanjana's baby? Who marries whom? Who Is Ranjana? What happens to the opposition gangsters? How does Don Muthuswami handle the police?