Aliens from the constellation Hydra crash-land on the island of Sardinia. A prominent scientist, his daughter, several young technicians, and a pair of Oriental spies are taken hostage by the beings so they can use them to repair their spaceship's broken engine. With that done, they take off towards their home planet, taking the earthlings with them. However, the humans attempt to mutiny against their captors, inadvertently sending their tiny spaceship hurtling into the infinite beyond...
| Actor | Role |
|---|---|
 Leonora RuffoKaena | Kaena |
 Mario NovelliIngegner Paolo Bardi | Ingegner Paolo Bardi |
 Roland LesaffreProf. Solmi | Prof. Solmi |
 Kirk MorrisBelsy | Belsy |
 Gordon MitchellMurdu | Murdu |
 Alfio CaltabianoArtie | Artie |
| LLeontine MayLuisa Solmi | Luisa Solmi |
 Nando AngeliniIngegner Morelli | Ingegner Morelli |
| GGiovanni De AngelisGiulio | Giulio |
 Mirella Pamphili(credit only) | (credit only) |
| JJohn SunDr. Chang | Dr. Chang |
| AAntonio HoChinese Secret Agent | Chinese Secret Agent |
| JJohn ChenChinese Secret Agent | Chinese Secret Agent |
 Pietro FrancisciHimself (uncredited) | Himself (uncredited) |
 Renato MontalbanoThe Doctor at the casualty department (uncredited) | The Doctor at the casualty department (uncredited) |
 Gianni SolaroThe Director of the Research Institute (uncredited) | The Director of the Research Institute (uncredited) |