Earth's defence forces are engaged in a losing battle with the evil Darkon. A ship plummets to Earth and explodes, and out walks a stranger, unscathed, but suffering from amnesia. In his possession is a Tekno crystal, which he can use to transform himself into Teknoman, an unstoppable fighting machine. As the war turns in their favour, they learn that Darkon is breeding Teknomen from captured Earth families - Teknoman must soon face his own brother in a battle to the death.