RADDITZ

The story of Dragonball Z starts with an alien landing on earth.  This alien, unfortunately, is not a little green man, but a tall humanoid from the race called the Saiyans or Saiya-jins.  This guy is quite unfriendly to everyone he meets, and has only one mission:  To find his brother Kakarot and figure out why he didn't destroy the earth.  He meets up with Piccolo, beats him around a little bit and then leaves, searching for Goku.  He meets up with the Z fighters at Master Roshi's island at Kame house.  Meanwhile, Goku is visiting his old friends at Kame house, showing them his little son.  Out of nowhere, the alien appears.  He addresses himself as Radditz, addresses Goku as Kakarot, and asks Goku why the planet wasn't destroyed. Goku, having received amnesia after a near fatal childhood accident, remembers nothing about this.  Radditz then yells at him, because he forgot his mission.  He then tries to convince Goku to come with him.  However, Goku doesn't want to be a Saiyan, so Radditz kidnaps Goku's son, Gohan.  Goku proceeds to fight Radditz, but loses.  Radditz flies away, Gohan in hand, waiting for Goku to come after him.  Goku, after being brutalized, stands up and notices someone he doesn't like to see, his arch nemesis, Piccolo.  Piccolo tells Goku that the only way to rescue his son and kill Radditz is to team up and fight him.  Goku agrees to go together, and they start flying toward Radditz's power source.  Meanwhile, Gohan is being taunted by Radditz, and is finally locked in Radditz's space ship.  Goku and Piccolo arrive on the scene and start to fight.  They start getting beat around by Radditz, so Piccolo tells Goku of a new technique he created.  He then tells Goku to try and grab Radditz's tail, since Goku being a Saiyan, remembers how bad it hurt when someone grabbed his tail. Goku manages to grab it, and Radditz screams with pain.  Meanwhile, Piccolo charges up his Makkankosoppo, or Special Beam Cannon while Goku holds his tail.  Unfortunately, Goku is too gullible, and falls for the hollow promises Radditz makes, so he lets go of his tail.  Radditz then starts laying the smack down on Goku, and manages to take Piccolo's arm off. Fortunately for Piccolo, he can regrow his body parts, so he regrows his arm.  Goku, on the other hand, is getting beaten by Radditz and Gohan can hear it.  He gets so pissed that he destroys the ship and bashes Radditz in the stomach, breaking his armor and decreasing his power level.  After Gohan uses his energy, Radditz is weak enough to be ambushed and that's just what Goku does.  He gets Radditz in a bear hug and tells Piccolo to charge up his Makkankosoppo again.  Piccolo gladly obliges, figuring that he can kill two enemies with one blow.  The beam ends up doing just that, killing Goku and Radditz and leaving Piccolo and Gohan the only survivors.  Piccolo thinks he won the fight, because they were both dead, but he makes one very bad mistake: He tells Radditz about the dragon balls, and tells him that they will just wish Goku back to life.  Piccolo, not knowing that Radditz's scouter is also a sort of walkie-talkie, unwitting sets the plot in motion.  Radditz tells him about the scouter and then dies, leaving Piccolo with the info that more Saiyans will arrive in one year.  Piccolo takes Gohan up as his student and offically becomes a good guy.

NAPPA AND VEGETA

While Piccolo is busy training Gohan, Goku is busy traveling Snake Way in order to reach King Kai's planet.  Along the way he falls off once, into Hell, and he has to trick two ogres into telling him how to get back on Snake Way.  Everyone on earth is busy training for the ominous Saiyan threat, up on Kami's lookout in a special room that lets them fight Saiyans from the past.  Everyone but Yajirobe is training then.  Goku is tricked into going into Princess Snake's palace, where he his almost eaten by her and her henchmen.