Gregory Swofford and Jessica Morgan, two scientists on a mission in space testing a heat resistant metal, come across a ship. Detecting a life sign, they find out that Optimus Prime is inside it. Gregory is very reluctant to bring Prime over, as a previous battle between Prime and Megatron resulted in his face getting scarred. The star the ship is near is about to go nova, but Jessica and Gregory head over to the ship. They find Prime now dead, but they bring his body back and move their ship away. Prime's ship explodes and the star goes nova. But Gregory and Jessica's ship is not damaged, meaning their new metal is a success. However they find it has been partially covered in some kind of spore. They return to Earth, where they meet Jessica's father, Mark. They test the spores on a rat, which becomes infected and immediately starts attacking another rat, infecting it with what they call a hate plague.

The Terrorcons then arrive at the lab, having been ordered to steal the metal. The Technobots arrive and try to stop them, but the Terrorcons form Abominus and destroy part of the roof. Jessica pushes her father to safety, but falling debris smashes her legs up. The Terrorcons find the metal and retreat, whilst Jessica is taken to a hospital. Gregory and Mark and furious with the Transformers, not caring that the Autobots were trying to help. Mark says he hates them all, but Gregory has a plan: resurrect Optimus Prime and infect him with hate plague, so he can then infect the other Autobots. They attempt to revive Prime, but can't do it.

Meanwhile, Jessica is seen to by the Autobots, who equip her with an exosuit to allow her to walk again. When Mark sees this he becomes even more enraged. He, Gregory and Jessica head back to the lab. Gregory intends to melt Prime's body down and use it to make more of the metal alloy, but Jessica begs him to stop. Gregory comes up with a new idea: lure the Autobots here to reclaim Prime's body, then infect them with hate plague. Mark agrees with this plan and tells his daughter to go and bring an Autobot here.

Jessica is taken to Autobot City by Ultra Magnus, where she explains to Rodimus Prime about what her father and Gregory intend to do. Rodimus decides to go to the lab, despite Jessica warning that's what her father wants. An Autobot strike team is made, who head straight to the lab. Ratbat has been listening in on the conversation, and reports this back to the Decepticons. Rodimus and Jessica head into the lab, but Mark doesn't seem to be around. They find Prime's body, which has been moved from the place Jessica last saw it. Realizing it's a trap, the two see that in the next room, a group of Autobots have been infected with the spores, which makes them turn on each other and fight. Things only get worse when the Decepticons arrive, who nearly all get infected -someone infected with the hate plague needs to only touch someone who isn't to infect them. Galvatron doesn't understand what's going on, so Rodimus explains it as he and Jessica leave with Prime's body. Galvatron decides this is no place for him, so he flees.

Superion heads to a city, where a group of Autobots attempt to stop him. He easily blasts them all down, then heads off and manages to infect Defensor. Rodimus brings Prime's body to Wreck-Gar and asks if he or the Junkions could repair him, but Wreck-Gar says it can't be done. Rodimus then contacts Sky Lynx and tells him to find a Quintesson -as they once revived Prime before, he hopes they can do it again. Rodimus then shuts down Metroplex, knowing the dangers of what would happen if he became infected. As he does this, Ultra Magnus appears, and starts chasing Rodimus.

Wreck-Gar tries to help Rodimus, but Ultra Magnus infects him. In turn, Wreck-Gar then infects Rodimus. Meanwhile, Sky Lynx saves a Quintesson from a group of infected Sharkticons, making a deal that the Quintesson must repair Optimus Prime. They go back to Earth, where the Quintesson works hard in repairing Prime. The Quintesson is almost done, but wonders what they'll do about the disease. Sky Lynx hopes Optimus will know what to do. The Quintesson activates a machine, causing Optimus to glow with a white aura. Optimus stands up, as Sky Lynx says their leader is back. Optimus tells Sky Lynx that this time, no force in the universe can stop him.

Notes

-The Secret Files segment for this episode is about the Autobots.

-SCRIPT DIFFERENCES: Click here for details.

-After the Transformers movie was released, there was a massive backlash against it due to the death of Optimus Prime. To appease fans, Hasbro decided to bring Optimus Prime back in this two part special. It seems these two episodes were made slightly later than the other season three episodes -all of the other episodes were first broadcast in 1986, but The Return of Optimus Prime was first broadcast in February 1987. The story for these episodes picks up right where Dark Awakening left off, but changes a ton of things. Mainly, at the end of Dark Awakening, the Quintessons are blasting Prime's ship with everything they've got, but are completely absent here. Optimus was really battered by the end of Dark Awakening, but looks brand new at the start of this episode. Presumably, as Dark Awakening had already been made, the writers had no other option but to retcon parts of it to get these two episodes to work story wise.

-The shot showing Prime's ship exploding is taken directly from Dark Awakening.

-Despite them first appearing late on in the second season, this episode marks the first time that Streetwise and Groove are actually called on by name.

-It also marks the debut of the Throttlebots, who aren't named and immediately get infected.

-The hate plague seems to have an odd effect on Transformers. Whilst it does make them fight at first, some of them, like Ultra Magnus, seem to calm down a little and start trying to just infect others. For example, when Magnus finds Rodimus in Autobot City, he doesn't try to hit him, rather, he just tries to touch him. Brawl can be seen doing the same thing to Headstrong later on. The Sharkticons can also be heard yelling "infect them all!" when they chase after the Quintesson. We'll get to see more of this behavior in the next part. Also odd is how the infected Aerialbots are shown working together to combine into Superion.

Errors

-During this shot, the rats are colored red, but they haven't been infected by hate plague yet.
-When Mark and Gregory run through the hospital, this shot has Swindle stood among the Protectobots.
-When the Protectobots transform into Defensor, his left arm is missing... a callback to this episode perhaps?
-Ratbat is colored completely white when he returns to Soundwave.
-Seconds after the above, when Soundwave turns his head, there is a layering error with his mouthplate.
-Ratbat's recording only has Jessica state "my father has his body in the lab". Somehow Galvatron immediately knows she's talking about Optimus Prime.
-When Superion transforms back to the Aerialbots, Goldbug is seen standing in front of them. Goldbug hasn't been made yet!
-When Rodimus drives off, he avoids three Transformers. The middle guy is Wildrider, who shouldn't be there as the Decepticons haven't arrived yet.
-The canister Mark throws is initially colored gray, but changes to red in all other shots.
-When Galvatron says they've come for Optimus, Bruticus is really small, and his right leg is colored red instead of yellow.
-The Autobot insignia on the front of Rodimus is missing during this shot.
-Rodimus' front window is colored maroon during this shot.
-The beam Defensor hits Superion with is initially colored red, but changes to gray.
-When Wreck-Gar gets infected, Rodimus is colored like he's infected too.
-Optimus Prime's mouthplate doesn't move for his only line in the episode.