Rani Mehra (Kangana Ranaut) is an under-confident young woman from Delhi. Two days prior to her wedding, her fiancé Vijay (Rajkummar Rao) tells her that he no longer wishes to marry her. He explains that his lifestyle has changed after living abroad, and her conservative habits would be a wrong match for him. Stunned at the development, Rani shuts herself in her room for a day. Wanting to take control of the situation, she asks for her parents permission to go alone on her pre-booked honeymoon to Paris and Amsterdam. After initially hesitating, her parents agree, thinking that a vacation might cheer her up.

In Paris, Rani meets Vijayalakshmi, who also calls herself Vijay (Lisa Haydon), a free-spirited woman of French-Spanish-Indian descent, who works at the hotel in which Rani stays. Overwhelmed by the new city and having gotten into trouble twice - once with the local police and once with a robber - Rani intends to return to India. However, Vijayalakshmi helps her out and gives her a tour around the city. The two have a series of adventures, during which Rani relives the memories of Vijay patronising her and forbidding her from dancing and drinking - which she's free to do in Paris. During one particular incident, Rani tries on what she considers to be a revealing outfit and accidentally sends a selfie of her wearing the outfit to Vijay instead of Vijayalakshmi. She quickly realises her mistake, but unbeknownst to her, the selfie prompts Vijay to begin searching for her.

Eventually, the time comes for her to bid an emotional farewell to Vijayalakshmi and board the train for Amsterdam. However, when she arrives in Amsterdam, she finds to her horror that her hostel room is being shared with three guys: Taka from Japan, Tim from France and Oleksander from Russia. Despite being skeptical of the boys, she soon becomes good friends with them, and spends time shopping, sight seeing, visiting a sex shop, and meeting pole dancers in a club. At the club, Rani befriends a pole dancer, Roxette.

Rani slowly begins to gain confidence by taking control of her decisions. She also realises her cooking potential by winning a cook-off by selling gol gappas (an Indian street snack). She learns more about her friends' backgrounds and begins to understand how different life can be for people in other parts of the world. One day, the four find Vijay waiting for Rani in front of the hostel. Vijay apologizes to Rani and asks her to reconsider the relationship. Their conversation escalates as he tries to grab hold of Rani, but her friends retaliate, and she tells him to leave. The two meet up the next day to discuss the future, but Rani leaves abruptly, saying that she would rather speak to him after she returns to Delhi. She then meets up with her friends one last time at a rock concert she had previously chosen not to attend. After bidding an emotional farewell to them, Rani returns to India.

Back in Delhi, Rani visits Vijay at his home. Vijay thinks that she has decided to forgive him. Instead, Rani hands him her engagement ring and after saying "thank you", she walks away with a smile on her face.

Saajan is a lonely accountant about to retire from his job. Ila is a young wife seeking her husband's attention, looking for ways to put romance back in her marriage, and tries to cook her way to her husband's heart. A neighbour who lives in the apartment above her gives her advice on cooking and marriage through shouted instructions. Through a rare mixup of the famous "dabbawalas" (a complicated system that picks up and delivers lunches from restaurants or homes to men at work) of Mumbai, the lunchbox with the delicious food Ila prepared for her husband instead gets delivered to widower Saajan. When the lunch containers are delivered back to Ila empty, she is happy, thinking her husband had enjoyed her cooking. When she questioned him, he did not seem to think much of it. Realizing the mistake of the delivery, she writes a note to the recipient of her lunch thanking him for enjoying the food and sends him her husband's favorite meal the following day.

Saajan replies saying that the food was salty. Upon advice from her neighbour, who believes the lunch went to Ila's husband, she responds by using hot chili in a lunch that turns out to be so spicy that Saajan resorts to eating bananas to help cool off his mouth. An exchange of the messages sent back and forth with the lunches ignites a friendship between Saajan and Ila who share memories and thoughts in notes passed back and forth in the lunch pails. Meanwhile Saajan deals with a young employee, Shaikh, he is supposed to train to replace him when he retires. Shaikh appears immature, annoying, lazy and irresponsible. On her end, Ila feels her husband is very remote. He not only complains about her food (which is delivered to him from the restaurant Saajan has ordered his lunches from), but she finds out he is having an affair. Also she supports her mother as her father suffers from lung cancer.

As Saajan and Shaikh get to know each other, Shaikh reveals that he is an orphan and has worked in several places, including Saudi Arabia. He is currently living with his girlfriend. As he rides the train home each day after work, he chops vegetables for their dinner on his portfolio. As Saajan trains Shaikh, he has told him what to do and left him on his own, but Shaikh had bluffed his way into the job and many mistakes come to the attention of the boss who calls both of them into his office, puzzled that, after decades of service with never a mistake, so much had gone wrong. He chastises Saajan but tells Shaikh to leave. Saajan takes the blame for all that has gone wrong and saves Shaikh's job. This act moves Saajan and Shaikh to have a true friendship prompting Shaikh to invite Saajan to dinner at his home with his girlfriend and asking him to be his best man in his wedding, since he has no one else to stand up for him and no family.

In their correspondence through the lunch containers, Ila mentions that Bhutan is a poor but happy and beautiful place where the cost of living is much less than India. Saajan contemplates moving there with her upon his retirement and writes back asking if she will be ready to move to Bhutan with him. Ila writes back saying they should meet and suggests a popular food joint. She is there at the appointed time but Saajan doesn't turn up. A dejected Ila sends an empty lunchbox the next day. Saajan writes to her saying that he did arrive, but did not meet her because he saw how young and beautiful she is and considered himself too old for her and advises her to move on.

Ila's father dies and as his body is taken away, Ila's mother confesses to her that she has been unhappy for most of her marriage. This helps Ila to feel released. She decides to search for Saajan by asking the address where the dabbawalas sent her food and goes to Saajan's office to meet him, but there she learns that he has retired and headed to Nashik. Ila writes a last message saying farewell to Saajan announcing that she will leave her husband and go to Bhutan.

The movie comes to an end with Saajan returning from Nashik and going in search of Ila with the Dabbawalas song being played in the background.