Piku Banerjee (Deepika Padukone) is a Bengali architect residing in Delhi, along with her 70-year-old father, Bhashkor (Amitabh Bachchan). Bhashkor has problems with chronic constipation and traces every problem's root to his bowel movements. His habits often lead to quarrels with the servants Budhan (Balendra Singh), and also irritates Chhobi Mashi (Moushumi Chatterjee), who often visits them. Piku loves her father and, as her mother has died, takes good care of him, but gets extremely irritated with him at times because of his eccentricities. Bhashkor has many medical tests done, but everything comes out to be normal, severely disappointing him. Bhashkor has recently fired the house maid, ignoring Piku's vehement objections, for stealing Phenyl, a charge that the maid opposes. This is the 5th maid that Bhashkor has fired in the last 2 months.Piku partner at work, Syed Afroz (Jisshu Sengupta) is a good friend, and she is a regular client of Syed's friend, Rana Chaudhary's (Irrfan Khan) taxi business. Piku's company uses Rana's taxi to commute her to the office, but Piku is notorious for being a very difficult customer. Piku criticizes the drivers with excessive back seat driving, due to which they lose focus and crash the car. Rana has his own family problems with his mother and sister. Rana's sister stole her mother-in-law's jewels and gave it to her mother. As a result, her husband has now left her.Bhashkor is opposed to the institution of marriage & wants Piku to take of him, to satisfy her maternal urge. Bhashkor says that marriage is a low IQ decision, and he says that wanted Piku's mother to be independent, but she wasted her life in the service of Bhashkor. Bhashkor criticizes Chhobi Mashi for marrying three times and says that her own daughter Eisha (Rupsa Banerjee) was never a priority for her.Piku goes for a date with Aniket (Akshay Oberoi), but Bhashkor keeps interrupting her saying that he has a fever, and makes such a fuss that Piku has to call up the doctor and talk about Bhashkor's feces texture and temperature. Aniket loses all appetite. No driver at Rana's company wants to take Piku's duty due to her irritating nature. Rana complains to Syed, but Piku brushes both of them off. Piku is offended by Rana's rude nature and tells Syed that she is taking a break from office. Despite all her irritation, Piku cares a lot for Bhashkor. Bhashkor has a bit much to drink at Chhobi Mashi's anniversary party and the next day his BP drops and he has to be given oxygen. Piku is distraught.Bhashkor's relative Nabendu (Aniruddha Roy Chowdhury) comes from Kolkata to secure his consent to sell the ancestral home. Nabendu says that a developer is interested in the land and is willing to pay top rates. Piku wants to sell their ancestral home in Kolkata, Champakunj, but Bhashkor objects vehemently, and decides to go to Kolkata. Piku has to comply in accompanying him, since she cannot let him travel alone. Bhashkor cannot fly due to his breathing problem, and he doesn't want to take a train as he gets constipation due to all the rhythmic movement. Bhashkor decides to travel by road, as he can stop wherever he wants and get some blood circulation going in his body. Due to Piku being very problematic with other drivers of Rana, they back away before Piku's trip. Piku, disappointed with the taxi agency, decides to book a flight, but soon, Rana arrives at their home to take the family to Kolkata himself, without informing his family about the trip. Rana is puzzled when he finds loads of luggage being loaded to his taxi, along with a lavatory chair for Bhashkor. He refuses to drive with Budhan in the front seat and only agrees when Piku sits in the front.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. Piku finds a large knife in Rana's boot. Bhashkor insists that Rana has to throw the knife away else he would not sit in the car. Rana pleads that the knife was kept by drivers for their safety on the highway. Eventually Rana has to compromise and throw the knife away. During discussion, Rana reveals that he is an engineer and had a job in civil construction in Saudi. He was made to work as security guard on the site, despite being offered a job as project manager. When he protested, he was fired. That's when he returned to India and managed his father's business.They spend the night in Varanasi where Rana shares a room with Piku and Bhashkor, as all other rooms are full, and he refuses to sleep in the car. Upon Rana's suggestion, the next morning Bhashkor tries India toilet sitting style, which doesn't seem to help either. 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 in the city and gradually grow close. He also subtly hints not to sell the house during a discussion.Rana leaves Kolkata the next day and tells or rather requests Bhashkor to stop his eccentricities which he eventually listens to. Piku changes her mind and decides not to sell the house. Meanwhile Bhashkor's sudden desire to cycle increases as he cycles through a part of the city alone, leaving everyone tensed since he did not tell anyone about it. When Bhashkor returns, Piku berates him for eating street food and for being irresponsible, but he simply states that his constipation is cleared, and he needs to cycle every day. He also remembers Rana who had told him to eat everything and not be choosy and picky about food. Piku is secretly happy but does not emote much.The next day, everyone discovers that Bhashkor has died in his sleep, probably from sleep Apnea or cardiac arrhythmia. Piku states that he always wanted a peaceful death. She returns to Delhi, where she arranges Bhaskor's funeral. There, Dr. Srivastava (Raghubir Yadav), Bhashkor's doctor, reveals to her that Syed, too, has constipation and Bhashkor knew about it for a long time. A few days later, she pays up whatever due she owes Rana. She renames the Delhi house "Bhaskor Villa" in her father's memory, and the maid, who had left due to Bhashkor's tantrums, returns to work.