Years after the end of Dragon Ball Z, peace on Earth is threatened when Pilaf manages to summon the Red Shenron. The antagonist is accompanied by Goku, and by targeting him with curses that are mistaken for a wish, turns him into a child. This is how the saga of space exploration began before Dragon Ball GT.
The wish is granted, the dragon disappears and the spheres are seeded into the universe, and thanks to King Kaioh's warning, Goku finds out If he doesn't return the Black Star orbs to Earth within a year, the planet will be destroyed. Bulma and Gohan work hard to build a spaceship, and after much deliberation and subterfuge, Goku travels through space along with Trunks and his granddaughter Pan.
A quick stop at the planet Imecka where they meet Gil, a robot that takes over the functionality of the Dragon Radar after Trunks carelessly drops it. Unfortunately, their ship is taken away by the underlings of the tyrant Don Kir. After the spaceship is recovered, the three are searched for on the planet, and they are captured, only to free that world from the rule of Kir, whom Goku easily defeats himself.
Arriving on the planet Monmaasu, Goku, Pan and Trunks manage to find them the four-star sphereShe got caught on a giant's tooth. On Gelbo, on the other hand, they are trying by all means to help a small village get rid of Zounama, a monstrous creature that can cause earthquakes. Thanks to a ruse and the direct involvement of Trunks, who pretends to be the monster's future platoon, they manage to cut off his mustache, only to find out that he can only predict earthquakes.
The volcano near the village is about to erupt and Goku manages to stop the danger by throwing two powerful Kamehamehas. The villagers then give the protagonists the orb in their possession, but it comes stolen by one of the Parabara brotherswho does not hesitate to escape with his spaceship.
There Space quest saga narrated in the first 22 episodes of the anime of Dragon Ball GT, ends with the protagonists arriving on the planet Beehai and on the orders of Mucci Mucci to Parbara to also recover the other sphere possessed by Goku.