Watch Dragon Ball Z Movie 01: The Dead Zone full episodes English dub.
Other title: DBZ Movie 1, DBZMV1, Dragon Ball Z: Return My Gohan!!, Dragon Ball Z Movie 01: Ora no Gohan wo Kaese!!
Synopsis: Kami-sama's old nemesis's son has come to exact revenge on Kami-sama for winning the title of Earth's Guardian. After kidnapping Son Gohan and using the dragon balls to gain immortality, he has a final showdown with Goku.
More infor: Myanimelist, Wikipedia