The film begins with Michelle McNally (Rani Mukerji), a blind and deaf woman, visiting her former teacher Debraj Sahai (Amitabh Bachchan), who now has Alzheimer's disease, in a hospital. The film then flashbacks to the past to her childhood.Michelle was a girl who lost her eyesight and hearing after recovering from an illness at the age of two and exists in a black world where she is isolated in the darkness of her own existence, trapped by her inability to see, hear and express. She grows up becoming more and more frustrated by the black and dark world around her, making her a violent, uncontrollable eight-year-old child. Her parents, Paul and Catherine, are at their wits' end trying to control her, until one day the light shines through the end of the tunnel. Debraj Sahai enters their lives, an elderly alcoholic teacher for the deaf and blind, Debraj sees himself as a magician and is a disillusioned eccentric man. He takes it upon himself to bring young Michelle into the light. He uses harsh methods, although always for Michelle's long-term benefit. At the same time as Michelle suffers through and triumphs over her challenges, we also witness numerous other changes. Debraj begins to succumb to Alzheimer's, first forgetting the way out of the Principal's office and then forgetting Michelle. Debraj is in a mental hospital due to his almost complete inability to remember his past and even how to speak. Michelle visits him wearing her robe and we see glimmers of memory return as Debraj realises that she has graduated and even does a victory dance. The movie ends with a scene of Michelle amongst a crowd of people all dressed in black carrying candles walking towards a church. There is a voiceover of a letter Michelle has written to Debraj's friend Mrs Nair explaining that today was her teacher's first day of school, and that like hers, his alphabet began with B L A C K.