While repairing space bridges, Young Optimus and his crew find the AllSpark, source of life on Cybertron, which attracts the forgotten Decepticons. They crash land on Earth and inadvertently cause a technological revolution.
Autobots take on the giant nano-roach and Bumblebee befriends an adventurous little girl, the daughter of the man who found the remains of Megatron and started the technological revolution. AllSpark interacts with her.
Megatron continues to try and persuade Dr Sumdac to rebuild his body. A key component is Destronium, but given its instability, the nearest source would need to be transported quickly. Using a thief and an experimental speed-suit from Sumdac's facilities, Megatron may get what he needs, unless the Autobots can stop the speedy thief.
When Starscream, Lugnut and Blitzwing begin their invasion of Earth, Optimus Prime demands Sari hand over her key for safekeeping. This causes her to run away, only to end up in the clutches of Blackarachnia. Optimus begins to doubt his leadership even when the next stage of Megatron's plot to be rebuilt begins.