The Decepticons steal the key to the plasma chamber but when they try to open the chamber, the energy released blasts them and several Autobots to the distant planet of Nebulos, where another civil war rages. The Autobots decide they need an extra edge to defeat the Decepticons and they link with Daniel and four good Nebulons to become Headmasters. Unfortunately the Decepticons use the same idea and also combine their weapons with evil Nebulons to create Targetmasters. The Autobots and Decepticons clash in their most earth shattering battle to date, with their fates and the future of Earth and Cybertron hanging in the balance!