During one single day a number of life destinies cross one another. It becomes a night for the involved they will never forget, a night when the coincidences are going to change their lives forever.
The film is based on a series of immensely popular Swedish children's books, about the boy Bert, who is just hitting puberty and having the usual problems with it. But that's where the usual ends abruptly.
The ten year old Nisse suffers from acute asthma and is rushed to the hospital. There he meets Lelle who is a bitter, lonely and seriously ill twelve-year-old. Lelle, who never gets any visits treats Nisse kindly. Lelle inaugurates Nisse in his secret plan to build a giant Zeppelin and steal the food available in the hospital's underground reserves.
