A pair of scientists, Gregory Swofford and Jessica Morgan, test a new heat-resistant alloy coating their experimental spaceship Solaris near a raging sun. As they move closer, they notice something on the monitor. It's an Autobot ship -- carrying none other than Optimus Prime -- on a collision course with the very same sun. They pull him out seconds before the ship impacts with the sun and causes a terrific explosion, which results in the Solaris getting overrun with multitudes of red spores. Dr. Swofford is revealed to hold a grudge against Prime, as he was once facially scarred during a fight between Optimus and Megatron. Though it was Megatron's doing, Swofford persists in blaming Prime. Later, as Swofford and Jessica's father, Mark, examine the spores and find them to be alive, inducing hatred in the beings they contaminate, the Terrorcons attack their laboratory to steal the alloy. The Technobots strike back, but Jessica is seriously hurt as the Terrorcons escape with their plunder. Her legs are paralyzed, but the Autobots give her back the ability to walk with an exo-skeleton. Nevertheless, Dr. Morgan is blind with hatred for the Autobots, blaming them for his daughter's accident, and plots to lure them into a trap to subject them to the spores. Jessica is sent to inform Rodimus Prime of the recovered Optimus, and a task force is quickly assembled. However, though Jessica warns the Autobots of her father's trap, the rescuers become victims of an unexpected twist in Dr. Morgan's conspiracy and all but Rodimus, who flees with the erstwhile leader, are contaminated. Soon, the disease spreads to more Autobots, then to the Decepticons and the population of Earth as Rodimus gets hold of Wreck-Gar, hopeful that he might be able to reactivate Optimus. But there is nothing the Junkion can do. However, as the tainted Ultra Magnus, having chased his leader without pause, infects Rodimus and Wreck-Gar, Sky Lynx rescues a Quintesson from contaminated Sharkticons in return for his help restoring Optimus Prime. A lengthy mending process finally results in the virtually impossible: Optimus Prime's revival.