Videl can't keep up with Gohan and Kibito, so she decides to go back. Before she leaves she realizes that Gohan was the kid who defeated Cell and not her father, and says that she will date him once he comes back. They follow Spopovich and Yamu to Babidi's spaceship. Babidi comes out, along with his new partner Dabura, the King of the Demons. After Spopovich and Yamu deliver the energy to Babidi, the wizard has no use for them, and he kills both of them.

Babidi enters the spaceship, but Dabura suddenly flies over to the Z Fighters, and he kills Kibito. Goku and Vegeta take some shots at him, but they miss. Dabura spits on Krillin and Piccolo, turning them both to stone. The only way to revive them is to kill Dabura. This lures the warriors into the ship. Upon arrival, they meet Babidi's henchman, Pui Pui, who tells them that they must fight a different opponent on each level of the spaceship, and as they are beaten up, their energy will be absorbed by the room and injected into the ball that contains Buu.

Vegeta starts to beat up Pui Pui with no effort. To give his fighter the advantage, Babidi changes the room to mimic Pui Pui's home planet, where the gravity is ten times that of Earth's. Unfortunately for Pui Pui, Vegeta trains at five hundred times of Earth's gravity, and he easily destroys Pui Pui. They move on to the second level where Goku will fight Babidi's pet monster Yakon.

Goku and Yakon start to fight. Goku is obviously stronger than Yakon, so Babidi changes the environment to mimic the Planet of Darkness, which is Yakon's home planet. To help himself see, Goku becomes a Super Saiyan. Yakon, the devourer of light, sucks up the light emitting from Goku. Seeing this, Goku again becomes a Super Saiyan, allowing Yakon to suck up all the light energy he can. Finally, he becomes a Super Saiyan 2 and gives off a flash of brilliant energy which is too much for Yakon to handle. Victorious, the fighters head to the next level.

The fighters move to the third level. This time, it's Gohan's turn to fight. Dabura decides that he will fight this time, but first he goes to the meditation chamber to prepare. Meanwhile, back at the World Martial Arts Tournament, only five fighters remain because the rest of them flew away. Hercule decides to finish the tournament with all five remaining fighters in the ring at the same time. 18 takes out one of them, and Mighty Mask, composed of Goten and Trunks, takes out another. Now it's down to those two and Hercule.

18 and Mighty Mask (Goten and Trunks) start to fight, and because they are able to use their arms and legs simultaneously as Mighty Mask, they have the upper hand against 18. But when she steps up the intensity, they can't keep up with her, so they decide to turn into Super Saiyans. This, of course, blows their cover, and they are disqualified as teams are not allowed in the tournament as Goten and Trunks are forced to flee. Now it is down to 18 and Hercule. Meanwhile, Dabura has finally finished his meditation, and is ready to fight Gohan.

18 gets Hercule in a headlock, and she uses the opportunity to cut him a deal: she'll throw the match if he pays her double what he wins for the title. He reluctantly agrees, and the fight soon ends with Hercule as the victor. Over in Babidi's spaceship, Dabura finally emerges ready to fight. Babidi sends them to a planet similar to earth so their fight won't damage the ship. As their battle begins, Gohan finds that Dabura is a tough opponent, so he revs up his power to Super Saiyan level.

Gohan and Dabura continue fighting, and from the outset it is clear that Gohan has lost his edge after not training for seven years and as a result is weaker than when he fought and killed Cell. Nonetheless, Gohan is fighting Dabura to a stalemate. However, his lack of fighting sense and inability to gain an advantage on Dabura causes Vegeta to begin to lose his cool, especially when Dabura begins to pressure Gohan in the fight. Noticing this, Dabura tells Babidi to return them all to the ship. He privately informs Babidi that Vegeta has a terrible rage burning inside him, and that he could be made to serve their purposes. Meanwhile, Goten and Trunks see Videl flying back to the stadium, and she tells them all about what's happening. Excited at the prospect of seeing magic and a wizard (although they reveal that they don't even know what a wizard is), they race off after the others.

Goku, Gohan, Vegeta, and the Supreme Kai are left wondering why Dabura suddenly stopped the fight. Vegeta berates Gohan for not defeating Dabura and Gohan realized that Vegeta should've fought Dabura and then Krillin and Piccolo would be restored to normal. Vegeta decides to blow up the ship and Supreme Kai begs him not to and Vegeta refuses to listen and Goku stops Vegeta. Supreme Kai then realizes that Vegeta is the new recruit that Dabura was talking about. Suddenly, Babidi tries to take over Vegeta's mind. Although he is urged to fight it, Babidi's magic is too strong, and Vegeta's impure heart gives in. Now with Babidi's "M" on his forehead, he has turned evil. Babidi transports them all back to the World Martial Arts stadium where he instructs Vegeta to kill his friends. Vegeta refuses, as he apparently has not lost complete control of his mind. He says that his only goal is to fight Goku. To bait Goku into fighting him, Vegeta destroys part of the stadium and several city blocks, killing thousands.

Goku refuses to fight Vegeta, so Vegeta destroys another part of the stadium. To avoid any further casualties, Goku reluctantly agrees to fight. The Supreme Kai tries to stop him, but he sees that it is no use. Goku tells Babidi to transport them far away from people, and the wizard obliges. The Supreme Kai and Gohan decide to break into the next level of the ship and try and stop Babidi. To avoid this, Babidi commands Vegeta to kill the Supreme Kai, but Vegeta refuses. Though Babidi is possessing him, Vegeta can only focus on one thing: fighting Goku. Goku gives Gohan one of the last two senzu beans before he and the Supreme Kai go further into the ship. Vegeta and Goku power themselves up to their maximum level, and are ready to fight.

Goku and Vegeta start to fight, and their raw power is astounding. Both fighters possess incredible ability, and so far, the fight seems to be a draw. Vegeta is able to lock Goku to a boulder with cuffs made of energy. He tells Goku how he has stolen his royal destiny by beating Frieza and becoming a Super Saiyan first, and how insulting it was to be surpassed in power by the child Gohan. Goku is able to break free, and the battle resumes with crushing force. Meanwhile, Gohan and the Supreme Kai have made it all the way to Buu's ball, but Babidi and Dabura are waiting for them.

Goku and Vegeta continue their battle. Vegeta reveals that he knew he could never surpass Goku's strength, so he allowed himself to be taken over by Babidi. He had seen what it had done to Spopovich and Yamu, and he wanted the power for himself. He also says that he wanted Babidi to reawaken the evil in his heart. Over the years, he had become like a normal person; he had a wife and a son, and thought the Earth was a nice place to live. He wanted Babidi's magic to free him from "those petty attachments", but Goku doesn't believe him. Meanwhile, before Gohan and the supreme kai can stop Babidi, Buu has finally gathered enough energy, and has begun to hatch.

In an attempt to abort the hatching, Gohan begins firing Kamehameha waves at the ball, but it doesn't seem to do much good. The ball opens, but after some pink steam escapes, there is nothing left in the ball. They believe that Gohan destroyed Buu with his energy blasts, but suddenly the pink steam begins to congeal. It forms into Majin Buu. Instead of a fearsome beast, Buu is a fat, pink child, but the Supreme Kai knows that it is really Majin Buu and not something else. Goku and Vegeta have noticed the sudden upsurge in power, and realize that Buu has been hatched.

Dabura insults Majin Buu, and with a single blow, Buu dispatches with the King of the Demons. Goku and Vegeta feel Buu's surge of power, and Goku convinces Vegeta to postpone the fight until they can take out Buu. Vegeta says he doesn't want Goku distracted while they're fighting. As Goku is preparing to leave, Vegeta knocks him out with a blow to the head and takes the final senzu bean, and promises to kill Buu himself. Babidi's first order to Majin Buu is to kill Gohan and the supreme kai. Gohan grabs Shin and takes off, but even with their head start, Buu catches up to them with blinding speed. With a single blow, Buu puts Gohan out of commission, leaving the Supreme Kai unguarded.

The supreme kai defends himself as best he can against Buu, but he is no match for him. Buu pounds the supreme kai into the ground, and is preparing to eat him when Gohan flies in and knocks Buu away. Gohan's recovery is short-lived, because Buu hits him with an energy blast of incredible power. As Gohan falls to the Earth in a forest, he is very badly injured. Goten and Trunks arrive at the outskirts of the scene and notice the "statues" of Piccolo and Krillin. Trunks accidentally breaks the Piccolo statue. As Buu is preparing to eat Shin, Dabura suddenly throws a spear through him. Dabura warns Babidi that he will soon lose control of Buu and his monster will turn on him. Babidi doesn't believe him, and now Buu's plans have changed: Dabura is next on the menu.

Dabura tries his best to destroy Buu, but he is nowhere near strong enough to do the job. Buu turns him into a cookie and eats him. With Dabura gone, Krillin and Piccolo, despite his statue being slightly broken, are able to come back to life. Just as Buu's about to eat the Supreme Kai, Vegeta makes his presence known by destroying Babidi's spaceship. Vegeta knows what Buu did to Gohan, and he vows that when Goku regains consciousness, this will all be over, even if it costs him his own life. He promises to atone for what he's done, and he powers up. At full strength, he ferociously attacks Buu.

Though incredibly powerful, Vegeta's attacks do nothing to Majin Buu. He even blasts a hole in the monster, but Buu is able to regenerate his body. Tired of playing around, Buu rocks the entire planet by powering up. He then rips off part of his own belly and is able to wrap it around Vegeta. Trapped, the Saiyan prince can do nothing to defend himself. Trunks can't stand to see his father tortured like this, so he powers up and jets off to help him, and Goten follows.

Trunks knocks Buu away from his father, and he and Goten free Vegeta from his bonds. Piccolo attacks Babidi, and despite the wizard using all of his magic to defend himself, Piccolo is able to slice him in half. Vegeta recovers, and tells Trunks that he is proud of him. For the first time, Vegeta embraces his son. He then knocks out Goten and Trunks, allowing Piccolo to carry them away to safety. With Buu back and ready for more, Vegeta makes the ultimate sacrifice: he erupts in a blinding flash of light, certainly killing anything near him, including himself.

After Vegeta's eruption, Piccolo returns to the scene of the battle. He finds no sign of Vegeta left, and that Buu has been blasted into thousands of small pieces. He also finds the top half of Babidi, who is begging for help. Suddenly, the pieces of Buu begin to reform. They all combine to make Majin Buu whole again. Knowing he's outmatched, Piccolo retreats. Buu heals Babidi, and the two embark on a killing spree. Piccolo catches up with Krillin, telling him that the world's last hope, Goten and Trunks, must be protected. Krillin is instructed to take the two young Saiyans to Dende's lookout. Meanwhile, the Supreme Kai has recovered, and is searching for Gohan.

Yamcha, 18, Bulma, Videl, and Chi Chi, among others, go looking for the Dragon Balls. Their search for the seventh one leads them to a nest full of eggs, but before Bulma can grab it, a dinosaur eats the entire nest. Yamcha hits the beast with an energy ball, which causes it to fly into the ocean. Videl goes swimming after it, and with a little help from Master Roshi, they are able to extract the ball. Piccolo and Krillin arrive at the lookout with the unconscious Goten and Trunks. Soon after, Goku regains consciousness and appears at the lookout himself.

While discussing tactics, Goku reveals that he knows of a method by which two similar-sized people can fuse together into one ultimate being. They decide that Goten and Trunks will learn this new trick, but the only problem is that it will take about a week to learn it, and Goku has less than a day left on Earth. Piccolo decides to teach the boys after Goku is gone. Suddenly, the sky turns black, and they realize that Bulma is calling the dragon. Goku uses Instant Transmission to appear at Capsule Corp., but she has already made one wish. Her wish was to bring back everyone that died today. Goku tells Shenron that they will postpone their second wish, and uses Instant Transmission to take everyone there back to the lookout with him. Meanwhile, Kibito awakens because of the wish, and the Supreme Kai is still searching for Gohan.

Kibito finds the Supreme Kai and heals him. Then, both of them find Gohan, and decide to take him to the world of the Kais. Meanwhile, back at the lookout, Goku breaks the news about Vegeta and Gohan to everyone, as both of them are believed to be dead. As expected, everyone is shocked; Chi-Chi faints after realizing that she has now lost both her husband and son, Bulma screams for Vegeta and breaks down crying, and Videl becomes heartbroken and cries, but refuses to believe Gohan is dead. They are just about to wake Trunks and Goten when Babidi suddenly starts a global announcement. He tells everyone that he and Majin Buu will terrorize the entire planet until Piccolo, Goten, and Trunks show themselves. To give them a taste of what's in store, he shows Buu turning the entire population of a major city into small candies, which he greedily consumes.

Babidi tells the Earth's people that anyone with any information about Piccolo, Goten, or Trunks should tell him. To stop any further damage, Piccolo wants to turn himself in, but Goku convinces him not to, because he knows that even if the three turn themselves it, it won't stop Buu's destruction. Goten and Trunks wake up, and they learn about Vegeta and Gohan's (supposed) demise. Goku is harsh with them, because they can't waste any time mourning right now. The boys, although angry at Goku for not saving Gohan and Vegeta, know that they must be tough to stop Majin Buu. In the world of the Kais, Kibito heals Gohan, and the Supreme Kai tells him about the Z Sword. It is a mystical sword that contains great power, and even the Kais themselves could not pull it from the rock it is now stuck in. The Supreme Kai believes that Gohan possesses the strength to do so.

Gohan attempts to free the Z Sword, but can't do it in his normal state. He transforms into a Super Saiyan, and with a mighty heave, he frees the sword from the rock. To his great surprise, the sword is incredibly heavy, and he must now train himself to use it. Back on Earth, Babidi and Buu continue their reign of terror, and Goten and Trunks tell him that they're going to destroy him and Buu.

Goten and Trunks begin their fusion training, but it is soon interrupted by Babidi. He announces that he has learned where Trunks lives, and he and Buu are now on their way to kill him. Goku sends Trunks to get the Dragon Radar from Capsule Corporation before it is destroyed, and he himself heads off to slow down Buu and Babidi. He asks Buu why he takes orders from someone as weak as Babidi. Though Buu seems intrigued by the thought of killing his master, he dislikes Goku as much as he does Babidi, so he decides to attack Goku. Goku knows that an ascended Super Saiyan isn't enough to stop Buu, so he says he'll take it up to the next level.

To buy as much time as possible, Goku demonstrates the Super Saiyan transformations. He starts in his normal form, then goes to Super Saiyan, then Super Saiyan 2. He then transforms into Super Saiyan 3, and the immense power of this transformation rocks the entire planet. His hair grows down to his knees, and his eyes change, and his eyebrows disappear. His power is so incredible that Gohan, the Supreme Kai, and Kibito can feel it in the world of the Kais. As a Super Saiyan 3, he possesses even more power than Majin Buu. He starts to pound Buu with relative ease. At Capsule Corporation, Trunks and Dr. Brief frantically search for the Dragon Radar.

Goku continues his awesome display of power, but with each blow to Majin Buu, the monster gets even more powerful. He seems to have an unlimited well of energy to use. Bulma calls Trunks on Videl's cell phone to tell him that she left the Dragon Radar in the airplane. He retrieves the radar, and heads back to the lookout. Goku senses this, and decides to end his fight with Buu. He once again tells Buu that he's much too skilled to be taking orders from Babidi. Goku Instantly Transmits himself back to the lookout. This time, Buu takes Goku's advice and turns on his master. He executes Babidi. Meanwhile, Gohan continues his training with the Z Sword.

Without Babidi to control him, Majin Buu goes on a spree of destruction. Trunks returns to the lookout with the Dragon Radar. Baba shows up to tell Goku that he only has thirty minutes left. His transformation into Super Saiyan 3 was very draining, and it ate up a lot of his time that was left. Even though he is exhausted, he begins teaching Goten and Trunks the Fusion Dance. On the world of the Kais, Gohan begins training with even more intensity than before, determined to save the universe from Majin Buu.

Buu clears some space in the countryside and builds a house for him to live in. Goten and Trunks continue learning the Fusion Dance, and begin to master the technique. They each plead with Goku for him to show them the Super Saiyan 3 transformation, and because he knows his time is up, Goku complies. Soon after the transformation, Baba shows up to take him away. Goku says goodbye to everyone, including Chi-Chi and Goten at the lookout and tells them that he will find Gohan in Other World, but Videl insists that Gohan is still alive somewhere. Once again, he is gone, leaving Piccolo in charge of training Goten and Trunks.

Back in Other World, Goku visits King Yemma to ask him if he's seen Gohan. King Yemma says that Gohan has not checked in. Thrilled that his son is still alive just like Videl said, he searches for his energy signal, and uses Instant Transmission to go there. He starts to help Gohan with his training with the Z Sword until Gohan is ready to fight Buu again. Piccolo continues training Goten and Trunks to fuse. Buu happens upon a blind kid named Tommy, who doesn't seem to be scared of him. Buu restores the kid's vision, but to his surprise, the child is not afraid of him. He is grateful that Buu made him see, and considers Buu a friend. Buu seems to like friendship more than fear.

Goku throws a giant boulder at Gohan to test his abilities with the Z Sword. Gohan makes a clean cut, so the Supreme Kai conjures up a block of the hardest metal in the universe called 'Katchin'. This time, the sword can't cut it, and breaks under the pressure. But from out of the Z Sword comes Old Kai, who is fifteen generations older than Supreme Kai. In exchange for a date with Bulma, Old Kai agrees to awaken Gohan's sleeping powers. He starts to do a strange dance in circles around the Saiyan, and says that it will take 5 hours to awaken his sleeping power. Meanwhile, Goten and Trunks have finally mastered the Fusion Dance, and are ready to attempt it for real.

Goten and Trunks attempt to fuse, and their first attempt yields a weird-looking fat kid with very little power. Their second attempt creates an old, emaciated weakling. Finally, the two are perfectly in sync, and make Gotenks. Piccolo tells him to wait thirty minutes for the fusion to wear off so they can try it as Super Saiyans. Gotenks thinks he's powerful enough already and takes off to find Majin Buu. He is able to get some hits in on the monster, but when Buu steps up the intensity, Gotenks is no match and is easily defeated. Meanwhile, on the world of the Kais, Old Kai continues the long ceremony needed to awaken Gohan's hidden power.

Goten and Trunks heal up from their injuries. They will train the rest of the day and fight Majin Buu tomorrow at full strength. On the world of the Kais, Old Kai has finished his five-hour ritual. Now Gohan must sit and meditate for twenty more hours for his power to awaken. Back at Buu's house, Hercule arrives to defeat the evil creature. He tries some tricks with poison candy and exploding video games, but they have no effect on the monster. Buu decides to be friends with Hercule.

Goten and Trunks successfully fuse as Super Saiyans, but once again, their ego takes over. Gotenks spends all of his time flying around the Earth at full speed, and by the time he decides to attack Buu, his 30 minutes are up. Back at Buu's house, Hercule is doing his best to please the monster. He even cooks him dinner. While away murdering people, Buu finds an injured dog and heals him. Buu discovers the joys of friendship with this dog, and when Hercule tells Buu that killing is bad, Buu vows never to kill again. But while Buu and his pet are playing fetch, two crazed gunmen shoot the dog.