Sidhant Rai (Rishi Kapoor) is a very successful and leading architect of the country. He lives in a huge palatial bungalow along with his three children Rohit, Rahul and Rani. Also living in his house are Casper (their pet dog), and an old family butler Baanke Bihari Chaturvedi - so called B.B.C. Sidhant's maternal uncles Vikram, Prabhakar and his brother-in-law Prince are also a part of the Rai household, and they are clearly disliked by the kids.

Being motherless from a young age, the three children of the Rai household are big pranksters, naughty and mischievous. Every time Sidhant Rai arranges for a governess or a master for them the children frighten or harass the poor teacher away. Sidhant Rai is in a very important meeting when he is informed that the children have driven away the tenth governor who came to look after them. He is very angry and excuses himself from the conference mid-way, and in a rage drives back home. Here he shouts at the children for being mischievous, but the butler reminds him of some past incident regarding scolding young children, Sidhant Rai mellows down and promises the kids that henceforth he will appoint no governess or master.

The three relatives of Sidhant Rai hold a small share in his business and when Sidhant becomes philanthropic about one project they try to stop him by saying that he is merely wasting his money. Sidhant however refuses to budge and the three have to forcibly agree to the project. Just as they are about to leave the phone rings and Sidhant says something about sending for her, the kids overhear the conversation and ask him who this person is, Sidhant tell them its their new governess, and though the kids accuse him of being a promise breaker he silences them by saying that if they as kids can break promises, then he as their father can do the same.

A small co-operative bank is being robbed by a small time thief Shekhar (Ajay Devgan) and his friend Jaddu, but on leaving the bank they are caught in traffic jam. In the same traffic jam, Shekhar sees Anna (Kajol), an orphan, who is now on her way to Sidhant Rai's house to look after the three children. It is love at first sight for Shekhar who with his con-act tries to convince her that he knows her, and even tells her that he is in love with her. Anna is shocked, but Jaddu covers up for Shekhar's action by telling Anna that she looks like his ex-girlfriend, and thus Anna excuses him.

As Anna moves towards Rai's palace she is being watched by Shekhar and Jaddu from a distance. Anna meets Sidhant Rai, and the children are introduced to her. She promises Sidhant Rai that she will tackle them well. Later that night they frighten her way. She runs out scared but then Anna, along with Sidhant Rai and the butler play tit for tat on the kids and scare them in the same way. However later a very crude prank is played on Anna by the kids when they send her a telegram announcing her parent's death. Anna is hurt and decides to leave. The kids realize their mistake and accept Anna as their elder sister and apologize to her.

Shekhar now with the help of Jaddu convinces Anna of his love and Anna too falls in love with him. The kids and the butler tell Sidhant Rai about Shekhar and Anna who decides to get them married. On the day of the marriage Shekhar is arrested by the police for being a conman convicted of many crimes. Anna is heart broken, betrayed and absolutely devastated and cheated. She decides to go away to the orphanage again. Anna leaves and soon after this the entire Rai family – Sidhant, the three kids with Casper leave to get Anna back.

The events that follow the three uncles in a position to claim their right over the property, who in the guise of guardians of the children ill treat them. However their plans to usurp Sidhant's property come to a halt when another adult heir is discovered - Sidhant's younger brother, Rajit Rai, who had left home when he was only eleven years old.

Who is this Rajit Rai? Will the uncles be successful in their plans? What happens next? See the movie on the big screen