Subterranian Secrets(Underjordens hemlighet)

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.