Mili is a story about a girl who has a dreadful ailment, still she's ever lively and spreads happiness in everyone's life. She becomes an inspiration to her new neighbour (Amitabh Bachchan) who is a drunkard and always depressed. With her cheerful ways she changes Amitabh and he falls in love with her. But he does not know of her ailment. When he comes to know about it, he thinks of going away as he cannot bear to see her die.