Autobot City is being attacked by Decepticons, the Decep Clones stole the key to the Plasma Energy Chamber leaving Punch badly damaged. The Decepticons retreated to Cybertron to open the Plasma Energy Chamber,and destroy some Autobots along with it. Few of the Autobots took the key back from Scourge and was launched to another planet called Nebulos. A little while after the Decepticons followed the Autobots, where they found them captured by the natives of Nebulos. So, the Decepticons captured half of the Autobots to find out the whereabouts of the key.
In order for the Autobots to save their comrades, they have to partner up with Nebulans to become Headmasters and Targetmasters. While all that is going on, Optimus Prime managed to go to Vector Sigma and found out the Autobots whereabouts also the deadly secret of plasma energy. So, Optimus used another shuttle to get key and his Autobots. By the time he got to Nebulos, the Autobots have already lost the key to the Decep Head & Targetmasters. Prime and the Auto Head & Targetmasters went to retrieve the key from them again, but finds a big surprise waiting to surface and show its ugly head "Scorponok".
Scorponok and the Decepticons fled Nebulos and went back to Cybertron. Optimus and the Autobots followed them back, but Spike insisted that him and Cerebros should stay. The Decepticons made it with the key and deactivated every Autobot on Cybertron, Prime and the others had got there too late. So they tried to find the Galvatron and stop but that plan failed. Galvatron has already activated the Plasma Energy Chamber, but he also failed when Spike and Cerebros arrived with "Fortress Maximus" and saved the entire universe from being destroyed.
"I hope this review is good enough."