Karan (Saif Ali Khan) is a cartoonist and a self-styled ladies' man. His daily comic, named "Hum Tum," explores the battle of stereo-typical behavior. On a plane from Delhi to New York, he meets Rhea (Rani Mukerji), but she doesn't seem the to be a least bit interested in him. His feeble attempts at flirting go nowhere, but when they have a stopover in Amsterdam on their way to New York, she agrees to spend a few hours exploring the city with him. Karan quickly learns he has little in common with the feisty but proper Rhea, but he won't give up. He ends their contentious time together with an unwelcome kiss. Rhea is outraged, slaps him, and storms off, but Karan insists they'll meet again. After a couple months living in New York, he spots her in the park, and she causes a scene with his girlfriend (Shenaz Treasurywala),who is Rhea's friend, this ends in the break-up between Karan and his current girlfriend.