The film opens with Piccolo being attacked and supposedly killed by a group of shadowed fighters. He couldn't have been killed, because Kami still was alive and fought Garlic. Chi-Chi along with her father, Ox King, and Gohan are attacked by an unknown group of warriors. Goku is out fishing during the attack and after sensing danger, he returns only to find his son has been kidnapped. The group responsible for the attack are Garlic Jr.'s henchmen, and it is later revealed that they were not so much holding Gohan ransom for any reason, but because they were after the four-star Dragon Ball that was attached to his hat. After retrieving the remaining Dragon Balls, Garlic Jr. summons Shenron and he immediately wishes for immortality. Shenron, never having to grant this type of demand before, grants Garlic Jr. his wish. A furious Goku arrives to try to take back his son, but soon discovers Garlic Jr.'s new power. Kami makes an appearance (which surprises Garlic Jr., who thought that his henchmen had killed Piccolo) and meets up with Goku, and describes a brief history of Garlic Jr. and his father Garlic. Goku then proceeds to try to find Gohan when he is attacked by the villain's gang, whilst Kami faces Garlic Jr.
After brief fighting, Krillin and Piccolo arrive to help. Piccolo gets revenge for being attacked earlier by defeating Garlic Jr.'s henchman Sansho, while Goku manages to defeat the other two henchmen Ginger and Nicky. Meanwhile, Kami is getting brutally outmatched by Garlic Jr., until Goku and Piccolo rescue him. And with Garlic Jr.'s newly obtained immortality and a new muscular second form, it seems not even Earth's warriors can take him down. But when Goku & Piccolo work together, two-against-one prevails, and Garlic Jr. is outclassed. Angry at his defeat, Garlic Jr. unleashes his ultimate attack, and bursting with anger, he opens up a portal known as the "Dead Zone". Intending to suck his enemies into the void, Garlic Jr. becomes frustrated with Goku's ability to avoid the Dead Zone, and he decides to handle Goku himself, and later force him into the Dead Zone. Things looking extremely difficult for Earth's hero, Goku's son, Gohan, becomes enraged witnessing his father and friends in danger and releases his latent energy, blasting Garlic Jr. into his own vortex to be trapped for an eternity. Remarkably, in the end of it all, Gohan doesn't remember a thing of what happened, instead believing that his father defeated Garlic Jr., and with amazement, Goku figures his son is no ordinary boy, but one with a great hidden potential. At the end of the film, Piccolo is seen from above, looking down on Goku and his friends and vows that one day, he will defeat Goku.