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.
| Release Date | February 22, 1991 | |
|---|---|---|
| Status | Released | |
| Original Title | Underjordens hemlighet | |
| Runtime | 1h 22min | |
| Budget | — | |
| Revenue | — | |
| Language | Swedish | |
| Original Language | Swedish | |
| Production Countries | Sweden | |
| Production Companies | SandrewsFilmTeknikCinetofonSvenska FilminstitutetSVT | |