The search for the spheres in space in the first arc of Dragon Ball GT He guided Goku, Trunks, and Pan to forbidding planets and then stayed apart to try to recover Gil, the robot who caught General Rildo's interest after absorbing the dragon radar. Thus began the saga of Baby, Second of Dragon Ball GT.
Goku and Trunks were imprisoned in the mutated machine base, where Pan manages to break in and tries to save her. However, General Rildo uses the technology at his disposal to copy the combat intel of the two prisoners in his Sigma Force, and once he learns of Pan's infiltration, he sends Natt to kill them. The girl manages to surprise the machine with a new technique, the Maiden's Rage, and at the same time Goku awakens.
Several robots merge into the Super Mega Cannon Sigma, which is easily stopped by Goku, who is soon joined by Gildo himself, who manages to capture and imprison him and Pan. Luckily, grandfather and grandson manage to break free while Trunks, freed from a metal plate in Dr. Mieu's lab, learning of the scientist's greatest creation: infant.
The three protagonists gather in the lab, where the little enemy activates, reverts to his original form and reveals that he hatched the whole plan, using the scientist as a pawn and revealing his goal: Taking revenge for the extermination of the Tsuurua technologically extremely advanced alien species committed by the Saiyans.
In the meantime, the protagonists managed to escape and continue the search for the spheres. In space, they see a spaceship in which a child is in serious condition. They then decide to take him to the next planet, Pital, for treatment. In reality, it is Baby who is capable of passing from one blow to another and who, more and more vengeful, is heading towards Earth to kill the other Saiyans.
The antagonist manages to take control of Goten first and then Goten to get to Vegeta. This time, the parasite's deeper manipulation leads to Baby Vegeta, ready for it spread the tsuuru parasites on earth. Back on the planet with Pan and Trunks, Goku faces off against his old friend whose powers far exceed Super Saiyan 3's. Luckily, Kibito Kai manages to save Goku from Baby Vegeta's Revenge Death Ball at the last second.
In the Kaioshin world, the Great restores Goku's tail, granting him an upgrade. Meanwhile, Baby Vegeta made a wish from the Black Star Dragon Ballsreviving the planet Vegeta, where Uub also goes, and by joining forces with Majin Buu, he tries to hold his own against Baby, who turns into chocolate after suffering one of his own attacks.
Back on the scene, Goku reaches a new level: the Super Saiyan 4, who controls the powers of transformation into Oozaru. However, Bulma, another of Baby's victims, has created a machine capable of increasing the villain's strength. The efforts of everyone including Gohan and Goten enable a Goku to throw a powerful Kamehameha x10 and finally free Vegeta from Baby.
The alien tries to escape on a ship that Goku promptly sends towards the sun and is therefore doomed to die. However, the danger is not over. The second wish expressed by Baby was the destruction of the earth, which is now inevitable. The Kai and Goku team up to teleport all residents to safetywhile Piccolo decides to stay on the planet to die and thus put an end to the powers of the Black Star Dragon Balls.
There Baby saga narrated from episode 23 to 40ends with the return of Earth due to the Namek Orbs, a party to celebrate Baby's defeat, and Gohan's remembrance of a great friend and mentor like Piccolo.