Piku Banerjee (Deepika Padukone) is a Bengali architect who resides in Delhi, along with her 70 year old father, Bhashkor (Amitabh Bachchan). Bhashkor has constipation problem and traces each and every problem's root to his bowel movements. Piku loves her father and, as her mother is no more, takes good care of him, but gets extremely irritated with him at times because of his eccentricities. Her colleague, Syed Afroz (Jishu Sengupta) is a good friend, and she is a regular client of Syed's friend, Rana's (Irrfan Khan) taxi business. Rana has his own family problems with his mother and sister.
Piku wants to sell their house in Kolkata, but Bhashkor objects vehemently. He decides to go to Kolkata himself to cancel the deal. Piku has to accompany him, since she cannot let him travel alone. Bhashkor brings up his constipation problem and decides to travel by road. Due to Piku being very problematic with other drivers of Rana, they run away before Piku's trip. Piku, disappointed with the Taxi agency, decides to book a flight but at the right moment Rana arrives to take the pair to Kolkata by road. Later in the movie we come to know that he hasn't informed his family about this trip.
On the way, the group encounters many incidents, including Rana on the verge of losing patience due to Bhashkor's fussy behavior and his constipation. They finally reach Kolkata, where Piku's relatives still live in the old house and Bhashkor asks Rana to stay for some time. Piku and Rana go out and gradually grow close.
Rana leaves Kolkata the next day, telling her that she has got a "very interesting family", and also subtly hinting not to sell the house. He also tells, or rather requests, Bhaskor to stop his eccentricities which he eventually listens to.
Piku announces that she has changed her mind and the house will not be sold. Meanwhile Bhashkor's sudden desire to ride a bicycle increases as he cycles through the city alone, leaving everyone worried. He returns with a packet of "kochuri" leaving Piku furious at him. He simply steps out of the toilet, stating that his constipation is cleared and he needs to cycle everyday. He also remembers Rana who had told him to eat everything and not be picky about food. Piku is secretly happy but doesn't emote much. The next day, everyone discovers that Bhashkor had passed away in his sleep. After his funeral in Kolkata, Piku returns to Delhi, where she pays up whatever due she owes Rana. Piku observes that parents, however irritating they become in their old age, should not be judged. A funny revelation is also made in the end that Syed has constipation and Bhaskor knew that for a long time. The movie ends on a happy note as the maid who had left in the early part of the movie due to Bhaskor's eccentricities returns to work.
