Kabir Grewal (Arjun Rampal), a Casanova film maker and screenwriter is making multiple films (GUNS Trilogy) based on a thief's life and robberies. All his films have been highly successful. In order to shoot the third part of the trilogy, he goes to Malaysia, where he meets a London-based film maker Ayesha Aamir (Jacqueline Fernandez). Kabir and Ayesha get friendly and soon fall in love. When Ayesha finds out about Kabir's Casanova attitude, she breaks up with him and returns to London. Dejected, Kabir goes into depression and returns to Mumbai, leaving his film incomplete. After several attempts, Kabir is unable to find the perfect climax for his film. On his assistant Meera's (Shernaz Patel) suggestion, Kabir attends a film festival as part of the jury, where Ayesha's film is being screened. Ayesha thinks Kabir is following her and asks him to stay away from her life. After his father's (Anupam Kher) death followed by him being sued by his film's financiers, Kabir decides to move on and complete his film.
In a parallel story, an infamous Roy (Ranbir Kapoor) is a mysterious international art thief whom no country seems to be able to get their hands on, including Detective Wadia (Rajit Kapur). On his new assignment, Roy goes to an unknown foreign land to steal an expensive painting only to find that its owner is the beautiful Tia (Jacqueline Fernandez). Tia lives alone in a huge mansion where the painting is kept. Hence, Roy tries to befriend Tia during an art auction and soon impresses her with his charm. Sparks fly between them and both start spending time together, giving Roy entry into the mansion. Looking for the right opportunity, one night Roy runs away with the painting, leaving Tia heartbroken. Roy later regrets, as he realizes he has fallen in love with Tia. He decides to return the painting to her. After a small clash with the painting's new owner, Roy manages to get it back. On receiving the painting, Tia realises that Roy is now a changed man and forgives him.
Meanwhile, Kabir's film Guns 3 is released and is hugely successful. It is then revealed that "Roy" was just an imaginary character in Kabir's film and Roy and Tia's story was actually the script of Guns 3. In the end Kabir proposes to Ayesha and they reunite, just like Roy and Tia reunite in Kabir's film. The movie ends with Roy and Tia walking together next to a bridge just like the painting Roy had stolen.
