The film starts with Daman Singh Bagga (Jimmy Sheirgill) and Usman Afridi (Piyush Mishra) being kidnapped by some Chinese goons and they're brought to Shanghai, China. Then the movie goes into a flashback. Happy (Diana Penty) and her husband Guddu (Ali Fazal) go to Shanghai, China for a concert. (Sonakshi Sinha) also known as Happy who is a Botany professor comes to Shanghai to join a university as a lecturer. At the airport the Chinese goons kidnap Happy 2(Sonakshi) mistaking her for Happy 1 (Diana). They take Happy 2 (Sonakshi)into custody and demand a contract as a ransom. The contract was actually given to Javed Ahmed and his son Bilal Ahmed (Abhay Deol), Who was friend of Happy 1 shown in the previous movie . The contract was given to their rivals So, they kidnapped Happy 2 ( Sonakshi) thinking she is Happy 1 (Diana) and that she could convince Bilal to give them the contract and as soon as she does this they will release her. Happy 2 (Sonakshi) is unable make them believe that she is not that Happy they are looking for and that they have the wrong Happy. Chang (Jason Tham), one of the goons does not believe her. Being left with no other options he abducts Bagga from his wedding ceremony in Amritsar and Usman from his farewell ceremony in Lahore. In the present moment in time.
Chang tells Bagga and Afridi to convince Happy 2 to do what they want her to do and convince Bilal into handing over the contract to them. But they soon learn that Happy 2 has run away. Meanwhile Happy 1 and Guddu reach the university and are told by authority to join the orientation programme. Clueless, they join the orientation and roam around the city. Meanwhile Happy 2 hides in a bar where she met Khushwant Singh Gill aka Khushi (Jassi Gill) who works in the Indian embassy. She hides in his car. After which he sees her and listens to her story , at first Khushi is not willing to help her but he finally agrees. He takes Happy 2 to his house.
The Next morning Khushi receives a call from Adnan who tells him he has kidnapped Happy2 to help him motivate himself into bringing him Happy1. Khushi goes to the others for helps, Bagga suggests that they arrange a concert to find Guddu. Aman takes responsibility to promote the event and FAQ arranges the concert. On they day of the concert Guddu and Happy 1 show up and they explain the situation to them. Guddu is not ready to help them but Happy 1 agrees as she believes that she is responsible for whatâ€™s going on. Meanwhile Happy 2 runs away from Adnanâ€™s custody. Unbeknownst to that Khushi and the others go to meet Adnan and his men. But Khushi understands whatâ€™s going on an starts to run away along with Bagga, Usman, Guddu and Happy 1.Happy 2â€™s Father finds out that Happy 2 has gone to China along with her cousins but has been missing for the past three days. Happy 2 finds Khushi and the others and follows them to catch Adnan and his gang they finally manage to catch them and hand them over to the police. Happy 2 and Khushi thank Happy 1 and Guddu for helping them. Happy 2 and Khushi are united and she finally meets her father. The movie ends in a scene showing Bagga flirting with Happy 2â€™s cousins and everyone laughing.