The existance of all Transformers, Autobot and Decepticon, is threatened by the awakening of the chaos-bringer. the mad demi-god, Unicron, has reared his ugly head - all must fear. Only the Autobot leader, Optimus Prime, realises the true extent of the threat. He has surrendered his Autobot forces to the Decepticon leader, Scorponok, hoping that he can persuade him, by example of his unprecedented capitulation, to join forces against the greater evil - that the Nebulan component within Scorponok (Lord Zarak) will surface... Meanwhile, a rebel Decepticon band, under the leadership of the ruthless Shockwave, have decided to usurp his authority. that's the situation on Earth - on the planet Hydrus Four, Grimlock has found the new potent life-giving fuel, Nucleon, and is in the process of reviving his deactivated Dinobot comrades...