Dragon Ball Z picks up five years after the end of the Dragon Ball series, with Son Goku now a young adult and father to his son, Gohan.
A humanoid alien named Raditz arrives on Earth in a spacecraft and tracks down Goku, revealing to him that he is his long-lost older brother and that they are members of a near-extinct elite alien warrior race called Saiyans (サイヤ人, Saiya-jin). Goku (originally named Kakarot (カカロット, Kakarotto) had been sent to Earth as an infant to conquer the planet, but suffered a severe blow to his head shortly after his arrival and lost all memory of his mission, as well as his blood-thirsty Saiyan nature.
Raditz tells Goku that along with two stronger elites, Vegeta and Nappa, they are the only remaining Saiyans after their home planet Vegeta was destroyed. Raditz asks Goku to enlist in helping conquering planets and joining the remaining Saiyans. When Goku refuses to join and help them, Raditz takes Goku and Krillin down with one strike, kidnaps Gohan, and threatens to murder him if Goku does not kill 100 humans within the next 24 hours. Goku decides to team up with his arch-enemy Piccolo, who was also defeated by Raditz in an earlier encounter, to defeat him and save his son. During the battle, Gohan’s rage momentarily makes him stronger than Piccolo and Goku as he attacks Raditz to protect his father. The battle ends with Goku restraining Raditz so that Piccolo can hit them with a deadly move called Special Beam Cannon (魔貫光殺砲, Makankōsappō; lit. “Demon Penetrating, Killing Ray Gun”), mortally wounding them both, and kills them after a short while. But before Raditz succumbs to his injuries, he reveals to Piccolo that the other two Saiyans are much stronger than him and will come for the Dragon Balls in one year.
