Karan (Tusshar Kapoor) and Natasha (Anita Hassanandani) are childhood friends. Natasha has always loved Karan, albeit secretly and wanted to marry him. Karan, however, falls for Tanya (Esha Deol), the new admission in college. Meanwhile, Professor Bakshi (Rishi Kapoor), who is rumoured to have murdered his wife and hidden her body, is reinstated at the college. When Karan blows hif Tanya, a playboy named Yash (Yash Tonk) befriends him and helps his way through Tanya's heart. To impress Tanya, Karan promises her that he will steal the exam answers from Professor Bakshi's house so that Tanya would pass easily.

Together Karan, Natasha and Yash along with two other friends, Pat and Kush, sneak inside Professor Bakshi's house to retrieve the exam papers so Tanya's year won't be a waste. When they find a woman's dead body there, they try to run away but are chased by Professor Bakshi. Their car accidentally hits Professor Bakshi and he falls down the cliff. Fearing arrest, they run away. Tanya is traumatized by these events, and leaves to start a new life.

Years later, Tanya, Karan and their group have a reunion at the wedding of one of their friends. However, a killer is lurking somewhere nearby and is waiting to strike. And one by one they start to die: Dolly, Pat and Kush are all killed, while Yash is attacked, but miraculously survives. Eventually, only three are left.

When Yash is attacked again, Karan follows who appears to be Professor Bakshi, only to find someone else being attacked while Bakshi is with him. He leaves to find Khush attacked, and Khush says "Tanya" as he holds a piece of red fabric.

Karan follows a car which has Natasha and Tanya in it to a cliff, and finds Natasha injured. She tells him that Professor Bakshi had brought her and Tanya here. Karan realises she is lying, as Professor Bakshi was with him, and also realises the piece of fabric Khush had in his hand came off Natasha's scarf. He asks Natasha why she attacked everyone, and she claims it because she loved him. She begs him to forgive her, but he is speechless. She says that after finding this out, he won't forgive her, so she walks backwards in the snow and falls off the edge, yelling Karan's name. He runs to save her, but is unsuccessful, and her scarf blows into his face.

On the first day of college, Karan remembers each of his friends who died, including Natasha. While on the plane back to Delhi, he meets Tanya again, and they decide to be with each other, while they find Yash in the back seat.

• Tusshar Kapoor as Karan
• Esha Deol as Tanya
• Anita Hassanandani as Natasha Twin Spirit / Tasu
• Vrajesh Hirjee as Pat
• Yash Tonk as Yash
• Johny Lever as Popatlal
• Rishi Kapoor as Professor Bakshi
• Manoj Pahwa
• Moon Moon Sen as Madam Sexena
• Jeetendra as Ravi, Karan's father
• Razzak Khan as hotel owner

The film's reviews were generally unfavorable, the film was declared flop by boxofficeindia.com. Critic Taran Adarsh gave it 1 star out of 5 and commented: "A poor copy of the Hollywood flick I Know What You Did Last Summer, Kucch To Hai offers nothing much except a few chills and thrills."

The film's soundtrack contains 8 songs, who which are all composed by Anu Malik and written by Sameer. According to the Indian trade website Box Office India, with around 9,00,000 units sold, this film's soundtrack album was the year's fourteenth highest-selling, however the song 'Ding Dong' became a rage.

• Main article: List of Bollywood thriller films