Nikhil (Sidharth Malhotra) is a struggling businessman, who thinks he loves Karishma (Adah Sharma), an actress. Nikhil is characterized as a person who believes that once you are committed to a girl, there should be no straying. Karishma asks Nikhil to arrange ₹50 million (US$780,000) before marriage, which is 7 days later, to earn a contract.
Nikhil meets Meeta (Parineeti Chopra), Karishma's younger sister, with whom he had a brief encounter 7 years ago. Meeta, who is an IITian in Chemical Engineering and PhD., is a super-intelligent geek with unusual behaviour and habits, who ran away 7 years ago to China after stealing money from her own father, leading to his heart attack. Now, just a week before Nikhil and Karishma's wedding, Meeta has turned up to meet her father, but Karishma is scared that her sister's sudden appearance might ruin their wedding. Hence, Karishma assigns Nikhil to keep Meeta away from her father (Manoj Joshi).
Meeta has returned with an intention to steal again but her involvement with Nikhil during the next 7 days diverts her attention. During these 7 days, with many personal and social activities, Nikhil and Meeta fall in love but Nikhil backs off as he doesn't want to betray Karishma. He comes to know that for her research, Meeta has taken a heavy loan of ₹100 million (US$1.6 million) from a Chinese investor by forging her father's signature. The deadline for payback is over and an extension of three days was given, during which she has to steal money from her father's account to save him from the investor's goons. Nikhil helps Meeta to hack her father's account but advises her to apologize to her family. Meeta reunites with her family and Nikhil realizes he is marrying the wrong girl.
Meeta is unable to gather the courage to steal her father's money and tells her father the truth. Her father forgives her and provides her with the money. Nikhil later tells Meeta on the phone that he should have gone with her to Goa when she asked him to come with her 7 years ago. Meeta tells him that it is not too late for them to run away.
When Nikhil comes to Meeta's house to run away with her, he sees Karishma with her family and returns home, realizing the complications. Nikhil later scolds Meeta for being so ready to run away and says that he cannot torture Karishma even though Karishma has emotionally tortured him throughout their relationship. Nikhil leaves Meeta and tells her to go away from here. Later that night Nikhil receives the call of his investor Mr. Adlani and gets the news that he liked his plan and is ready to invest in his plan.
On the wedding day, Meeta leaves her house without informing anyone except her father, leaving her mobile phone inside Karishma's room. Nikhil tries to call her and sends many texts, which go unanswered. On reaching the mandap Meeta's father informed him that she has already left for China. Karishma finds Meeta's phone in her room, reads the messages, and realizes she has lost Nikhil. During the wedding she asks Nikhil to leave the wedding, her decision is supported by her father. Meeta on the airport cries hard and tries to end her life but give up that decision and goes back to the wedding. The two reunite and express their love.
The movie ends with Nikhil and Meeta at the airport, scheduled to travel to Germany. Meeta tells him that there is another problem waiting for them.