The Autobots settle into their new home and learn about Earth culture and customs, all of the while defending Detroit from various threats. Megatron's disembodied head, which has been in Professor Sumdac's laboratory since the ship crashed, comes back online and manipulates Sumdac into building him a new body, pretending that he is an Autobot. Blitzwing and Lugnut arrive on Earth searching for Megatron, while Blackarachnia targets Optimus Prime, blaming him for her techno-organic mutation. New Transformers introduced in the first season include the Autobot Arcee (who only appears in Ratchet's flashbacks), the Decepticon Soundwave, the bounty-hunter Lockdown, and the Dinobots Grimlock, Snarl, and Swoop. Several human villains are also introduced, including Nanosec (who can run at extreme speeds), the Headmaster (who pilots a machine that attaches to and controls large robots) and Meltdown (who is covered in a toxic and corrosive substance). The season ends with Megatron returning with a new body (built by the all-powerful AllSpark from his old body), and the AllSpark exploding into many fragments that scatter across Detroit.