Bank receptionist Harleen Sahni (Katrina Kaif) leads a quiet life in snowy Simla with her grandmother (Kamlesh Gill). Harleen is shy and afraid of life, and manages to come across as the mousy girl that nobody notices, apart from the bank's new VP (Pratik Dixit), who makes an inappropriate pass at her. Finally, frustrated, Harleen makes a profile on a dating website, and since the movie is called Bang Bang! (2014), her life is bound to change one way or another.
The website matches her with one person, Vicky Kapoor, but he's late. Very late. However, when he does show up he's played by Hrithik Roshan, and he's kind of amazing. He's patient, he listens to her, and he even teaches her to dance so that she can join in the inevitable (and terrific) big musical number. A waitress spills a drink on Harleen so she slips away to the bathroom to clean up. While she's there, she convinces herself that this is her big chance to live life to the fullest, and she wants Vicky to be a part of it, but when she comes out he's already gone.
However the movie doesn't start with Harleen, it starts with Indian Army Colonel Viren Nanda (Jimmy Shergill), who arrives to take custody of international terrorist and criminal mastermind Omar Zafar (Danny Dengzongpa). It doesn't go well. Zafar's men arrive to free him, and in the process and despite his heroic efforts, Viren is horribly murdered while his mother listens on an open phone line.
Zafar wants to stir up some confusion (and put an end to a potential extradition treaty between the UK and India) so he offers a reward of five million dollars to any Indian who can steal the Koh-i-noor. Someone promptly steals it, and soon enough master thief Rajveer (Hrithik Roshan) is in snowy Simla to get paid and hand over the diamond. Zafar's enforcers try to double cross him, leading to a big fight and subsequent rooftop chase, and he ducks into a small cafe and spots Harleen sitting there alone, so he takes the place of her date. Everything's going well until he spots his pursuers approaching, so he ends the dance number and engineers a spilled drink to get Harleen out of the way for the big fight scene. When she comes out of the bathroom, Rajveer is gone, the police have arrived, the cafe is in shambles, and the manager hands her a large bill. She gives the manager her bank VP's card and leaves.
On the way home she runs into Rajveer again. Literally. With her car. He's not hurt too badly, though, and after she helps him sew up a bullet wound from earlier, he warns her not to trust anyone who comes looking for him, tells her where to find a gun to use to escape if she winds up in a car being taken to a "safe" place, then leaves.
Harleen tries to go back to her old life, but everything happens as Rajveer predicted. The police arrive, interrogate her, and decide to take her to a "safe" place, she finds the gun, and completely fails to intimidate anyone, then Rajveer arrives to rescue her and there's another huge action scene. Rajveer and Harleen escape to Pizza Hut, and after the product placement is done they go on the run, bickering their way through a globetrotting adventure with stops in Mauritius and Prague while Harleen tries to decide if she can really trust Rajveer. She probably shouldn't, because he's not really Rajveer either, and this isn't a heist movie, it's a spy movie.*
Bang Bang! isn't a part of the YRF Spy Universe, and it was never going to be; the film was made by a different production company, and both of the lead actors play different and pivotal roles in the Spy Universe franchise. It's a bombastic action movie with impossibly pretty people performing impossible stunts, but at heart, like the Spy Universe movies, this is a story about the need for human connection. Harleen wants to connect to the world outside her small life, and Rajveer has been deliberately cut off from the people he loves. They're both so desperate for connection that it's no surprise that they find it with one another.
The action scenes are ridiculous fun, the leads are (as mentioned) impossibly pretty, the jokes land more often than not, the romance is pretty good (though Rajveer tranquilizes Harleen more often than I am really comfortable with - there's always context but in the real world it's kind of a red flag) and of course the dance numbers are fantastic. Because really, why even cast Hrithik and Katrina in your spy movie if you're not going to let them dance.
(*Specifically, this is a spy movie that serves as an authorized remake of the Hollywood movie Knight and Day, which I have never seen.)