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.
Optimus Prime and the Autobots set up base at an old auto-parts shop. Meanwhile, Megatron's head comes back online and takes control of several robots to attack the Autobots and reclaim the AllSpark.
A scientist named Prometheus Black has a lab accident that turns him into Meltdown, a super villain secreting acid that melts anything. He goes after revenge against Sumdac and the Autobots.
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.
Bumblebee and Bulkhead are having fun celebrating their first-ever Halloween with Sari. That is, until the Decepticon Blackarachnia shows up to ruin their good times.
Continuing to use Dr Sumdac's naiveté to find a way to have a new body, Megatron helps the Doctor create a music-playing robot for Sari's Birthday, named Soundwave.
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.
