Dattatraya (Amitabh Bachchan) is a lively 102-year-old who lives his life to the maximum. Although he is 102 years old, his heart is that of a 26-year lad. He enjoys life and takes everything in a jovial way. Babu (Rishi Kapoor), his son, is exactly opposite. He believes that he is now too old to enjoy life and lives a routine life. Dattatraya wants to break the record of the oldest living person on earth, which is held currently by a Chinese man. He has to live 16 more years to do so. But in order to maintain his health to live that long, he has to stay away from negative minded people. Therefore, he decides to send his son to an old age home. Babu is very sad and worried to stay in an old age home as he is habituated to stay and sleep in his home since these many years. Dattatraya agrees not to send Babu to old age home on a condition that Babu has to fulfill certain conditions, which his father would impose on him on a regular basis.
The movie revolves around the conditions given to Babu, which he hesitates to fulfill initially but fulfills them due to the fear of going to the old age home. The conditions imposed on Babu change his way of looking at life.
The first condition is that Babu has to write a love letter to his deceased wife, Chandrika. After a lot of thinking, he submits the letter to his father, who laughs and enjoys reading the letter.
In the next condition, Dattaraya goes with Dhiru and Babu to Babu's doctor urging him to call the doctor a thief. Dattayara's idea was to break the connection between Babu and his doctor so that Babu stops going to the doctor's clinic every day for a checkup. Babu accepts the condition to stop going to the doctor's clinic every day without calling him a thief.
After completing few conditions, Babu starts seeing life in a jovial way, just like his father. One condition that totally changes Babu's life was when he sent him with Dhiru to certain parts of Mumbai which includes a visit to St. Sebastian's church. Babu starts to cry and seeing him Dhiru asks Dattatraya. Dattaraya answers that Babu & his son Amol regularly came here for prayers. But, when Amol grew up he asked Babu to send him to the USA for a brief time but instead settled there. He calls up Babu once in 6 to 7 months.
On Babu's birthday, Amol called up. Dattatreya, who considers Amol as nuisance & greedy and bad influence for Babu, doesn't answer the call and also doesn't inform Babu about this call. The same day, the flowers sent by Amol are intercepted by Dattaraya and not handed over to Babu. Amol calls up again at night but once again Dattaraya doesn't inform Babu about this call. He, in fact, deletes the call history from Babu's cell phone. The next day, Dattaraya hands over the flowers to Babu. Babu gets upset that these flowers were not handed to him earlier, and calls up Amol to thank him for his flowers. That's when Amol informs him about the 2 missed calls and also that he is coming to meet Babu next month.
Babu gets angry on Dattaraya for withholding this information. Dattaraya reminds him of the last 28 days of Babu's wife and the actions of Amol. Amol didn't even come to meet his mother citing lack of proper notice at his company. Then Dattaraya tells him about his last condition: he has to kick Amol out of the house. Babu disagrees.
After some days, Babu comes into Dattatreya's room and finds that he has several placards that say words about rebelling about Amol's entry into the house. To showcase the greediness of Amol, Dattaraya calls up Amol. He gets an auto-reply that Amol is unavailable and ends up recording the message that Dattaraya & Babu wants to discuss the property. Amol immediately picks up the call and Dattaraya convinces him to reach Mumbai on the 19th of that month. Babu still informs Dattaraya that he will not follow his last condition. Dattaraya starts reading Amol's letters which Amol had sent for Babu and was intercepted in between by Dattaraya. Each letter turns out to be materialistic and ends with "I hope you will understand."
The next day, Babu gives Dattaraya an affidavit that states that Babu is giving his share of the property to Amol. Dattaraya finally reveals that he has the brain tumor and doesn't have much time left to live. He wanted to change Babu and that old age home and breaking that record was just a set-up. Babu realizes that Amol is really greedy and Babu insults him and asks him to return to the USA from the airport itself. Dattaraya tells him that if there is an Amol then there is Dhiru also, indirectly asking him to accept Dhiru as the replacement for Amol.
Dattaraya tells Babu to blow a whistle when he dies, to celebrate his outstanding feat, 102 years. At last, 102 not out becomes 102 out & Babu whistles. Dhiru gives a recorded tape to Babu with a message that Dattaraya recorded 2 days before death. In that Dattaraya says that he is sitting in a cloud, with the Chinese man beside him. He is telling the man that the record will be broken by a man from his family, his son after another 43 years.