A year after the Universe 6 tournament, Vegeta has traveled to New Namek and used the Dragon Balls there to wish for his tail back. This confuses the other Z-Fighters, but Vegeta just says that he missed it. In actuality, Vegeta thinks the next evolution of the Super Saiyan will require this appendage. The Z-Fighters continue to train during this year.
One year later, Vegeta is meditating in space on a planet near the destroyed Planet Vegeta. He suddenly senses a fairly powerful ki coming from inside the planet. He decides to go and investigate it. He finds an entrance to the underground lair. As he searches for the ki signature, he finds a mysterious stranger waiting for him. The new fighter introduces himself as a Tuffle named Baby. He created a new body for himself to eradicate the Saiyans. Vegeta powers up to Super Saiyan 3 and tells him that he cannot allow himself to do this. Baby then powers up himself and dispatches Vegeta quickly. Baby then takes the defeated Vegeta and forces a strange looking earring onto his ear. The two fuse and become Fused Baby. Baby internally tells Vegeta that these earrings are a corrupted form of the Potara that allow the stronger fighter to have complete control over the fusion. Vegeta is powerless to stop him. Baby then flies off towards Earth, ready to kill the remaining Saiyans.
Goku senses a massive power level streaking towards Earth. It feels strangely similar to Vegeta’s, but too powerful and too evil. Goku and Raditz power up to meet the new foe. Fused Baby lands on Earth and immediately broadcasts himself to the world. Goku and Raditz appear at the scene and are aghast to find the strange Vegeta-like man. Baby explains what has happened and tells them that he is here to eradicate all Saiyans. Goku and Raditz have a plan to shatter the Potara and bring Vegeta back. Baby begins his attack on the two Saiyans. They are easily overpowered by even Baby’s base form. Goku goes Super Kaioken x20, which saps his energy quickly but allows him to push back Baby. Baby then goes Super Saiyan himself and crushes the two brothers. They are forced to retreat and get their friends and family to safety. Fused Baby begins searching for them, but he is hesitant to kill any humans unless absolutely necessary.
The Z-Fighters all meet up at Kami’s Lookout, but Baby is there waiting for him. He knew they would meet there, since he has Vegeta’s memories as well. The Z-Fighters launch a desperate assault against Baby, and their combined power enough to force him into Super Saiyan once more. Goten and Trunks fuse, and Gotenks manages to even fight semi-evenly against Baby with the others’ help. Baby then goes into his ultimate form: Ultimate Baby. At this point, only Raditz, Goku, Gotenks, and Daika are still able to fight. Baby walks over to Gohan and charges up a Big Bang Attack directly at his chest. In a flash, Goku uses the Instant Transmission to grab Gohan and get him out of there. Baby turns on Goku and begins to fight him, beating him violently. Raditz takes this opportunity to blast Baby’s earrings, but they do not shatter. Instead, one of them merely cracks, causing the fusion to become corrupted. Baby whips around and fires a powerful blast at Raditz, killing him. This causes Daika to go Super Saiyan 2 for the first time. Goku collapses, unable to battle. Gotenks unfuses due to the stress and time limit. Daika, Goten, and Trunks fight Baby with all their power. The corrupted fusion has less power than before, and the drain takes a toll on Baby. Eventually, the power of the kids overpowers Baby, and they completely break the Potara. Baby’s original form returns, as does an exhausted Vegeta. In a fit of rage, Baby begins to release all his power. Vegeta and Goku team up to finally take down Baby. They finish him off with a dual Dragon Fist - Final Flash. They then wish Raditz back with the Dragon Balls.