Kal - Yesterday and Tomorrow is about Bhavna Dayal and Maya Jalan who had been fellow collegians and close friends, both come from very wealthy families. Bhavna is in love with another ex-fellow collegian, Tarun Haksar, who also comes from a wealthy family, and is also in love with Bhavna. Their respective families' expect both to marry each other. However, Tarun and Maya suddenly announce their engagement, and get married, leaving a shocked and heart-broken Bhavna to deal with this situation on her own. She eventually breaks off all contact with her former lover and friend respectively.
One night, several months later, a disturbed Tarun returns to her life and apartment, and stays there overnight. The next day she is shocked to find out that Maya has been shot dead, and the police suspect Tarun of killing her. The question remains if Tarun had spent the entire night with Bhavna, then who killed Maya, and further why did Tarun decide to return to Bhavna's life all of a sudden?