Some Aerialbots start to have doubts about their cause, some have started to admire Megatron, and are thinking of switching sides. They get pulled into a time warp, and end up on Cybertron, before the current war began. They'll discover more about Megatron, and the origin of one of their own.

Failing to topple Megatron, an exiled Starscream plans his revenge. He uses World War II era machines and five personality components to create the Combaticons, which prove very powerful in their Bruticus form.

Optimus Prime is back and leads a team to Charr to retrieve the ship alloy from Galvatron. Galvatron guides them to it's location, but they confront a couple dangers and must fend off infected Transformers. Optimus and SkyLynx are the only ones not infected and barely get away with the alloy. The alloy is used to safeguard Optimus from the Hate Plague for his battle against Rodimus as the Matrix is the key to the cure.

The Decepticons acquire the Key that will give them access to Vector Sigma. After using Vector Sigma, they find the Key is also capable of making organics turn into machines. Megatron prepares to use it against Earth and The Autobots will need new allies in this battle, but their creation will come at a high price.

On the run from Galvatron, Spike, Daniel and several Autobots enter a mausoleum and find a surprisingly not dead Optimus Prime. This would be cause for great excitement among Autobots. Unfortunately, however, Optimus is really under Quintesson control and is being used in a plan against his friends.

While testing a new ship alloy, Jessica Morgan and Gregory Swafford (who hates Transformers) stumbled upon the ship Optimus Prime was on and saved him. Some time afterward, Jessica gets hurt in a battle between Protectobots, Technobots and Terrorcons, causing her father and Gregory to plot revenge. They use Optimus to lure the Autobots into a trap, getting them infected with Hate Spores which make them go berserk. As the infection spreads, Sky Lynx seeks out a Quintesson that could bring Optimus back to life.

The Decepticons acquire the Key that will give them access to Vector Sigma. After using Vector Sigma, they find the Key is also capable of making organics turn into machines. Megatron prepares to use it against Earth and The Autobots will need new allies in this battle, but their creation will come at a high price.

Both Autobots and Decepticons are facing tough times as they are in need of the element called Cybertonium. The Decepticons quickly get as much as they need, but the only way for the Autobots to get it is to rely on the Dinobots, who have been unaffected by all this. However, the Dinobots have been getting annoyed with the Autobots lately and leave them.

Omega Supreme reveals his past to Optimus Prime, which involves a city's destruction, Megatron and Constructicons.

Elita-1, leader of a group of female Autobots causing trouble for the Decepticons, is captured and used as bait to lure Optimus Prime into a deadly trap. However, Elita-1's strange time manipulation technique saves him, but leaves her close to death. Her only chance for survival lies in Alpha Trion.

The Decepticons discovers an old type of Decepticons, the Insecticons. They will ally to destroy the Autobots, who will have to face them in another great battle.

Megatron and a politician team up to slander the image of the Autobots.

While Megatron and Shawn Berger enjoy Decepticon Day in Central City, Spike tries to find video evidence that proves the Autobots are innocent!

Both Autobots and Decepticons are facing tough times as they are in need of the element called Cybertonium. The Decepticons quickly get as much as they need, but the only way for the Autobots to get it is to rely on The Dinobots, who have been unaffected by all this. However, the Dinobots have been getting annoyed with The Autobots lately and leave them.

Galvatron learns what has been going on recently and meets up with the Quintessons. Rodimus again looks for answers, discovering the bitter history between Quintessons and Transformers. The Quintessons created the Transformers, but their creations rebelled against them. And the Quintessons are eager to exact revenge.

Starscream, in Scourge's body, attempts to complete three assignments for the damaged Unicron in exchange for getting a new body.

The Decepticons have managed to construct a device that, once successfully tested, will allow them to travel to Cybertron. Later, they use a reprogrammed Bumblebee to make sure the Autobots walk into an ambush.

A battle with the Decepticons leaves Optimus Prime damaged. Several Autobots journey to Cybertron to retrieve a vital part that will help repair him, but the Decepticons take advantage of the situation and launch an attack.

The Constructicons, recently created for the Decepticons, have built a device to give Megatron the powers and skills of his soldiers. All this is to give him the advantage in a challenge he issues to Optimus Prime. And if Optimus loses, he and the Autobots must leave Earth.

Seeking revenge against Autobot and Decepticon alike, the Combaticons hijack the Space Bridge and use it to alter Earth's orbit, putting it on a collision course with the Sun. With the only means to get off-world damaged in battle, Optimus Prime and Megatron must race against time to stop the Combaticons before the Earth is destroyed.

The Constructions use the newly created Trypticon to battle Metroplex, who is still unable to transform, on Earth. Sky Lynx tries to get the needed cog for Metroplex, which is with Blurr and Wheelie, but gets into a fight of his own. The Autobots and Decepticons continue fighting on Cybertron, until the Quintessons manage to immobilize them, leaving only Spike to save the day.

The evil Primacron plans to use an energy being named Tornadron to defeat the Transformers and help in his universal conquest. Meanwhile, the animal form Transformers leave during a battle between Autobots and Decepticons upon getting a strange signal. The signal was apparently sent by Primacron's own assistant, who believes this group of ""Primitives"" can defeat Primacron.

Starscream is now in charge of the Decepticons, but all he does is lead them to defeat in battle against the Autobots. But things are about to get much worse when Megatron returns, setting his sights on a new and powerful anti-matter formula.

Natural disasters plague Earth as The Autobots attempt to stop Megatron's plan. A team of Autobots and Spike head for Cybertron to save Sparkplug, but they could be heading straight for a trap.

The Autobots on Cybertron evade capture and work toward finding a way to counteract the effects of the hypno-chips. Meanwhile, Optimus Prime leads the remaining Autobots in a battle to put an end to Megatron's plan.