Season 1 has episodes six through twenty-six of Transformers: Prime.
Following Megatron's supposed death, Starscream assumes leadership of the Decepticons. However, Megatron is found barely alive in the wreckage of the Space Bridge, and returns to power after a long period in stasis. Over the season, Starscream finds his life falling apart almost entirely due to his treachery with Megatron, and eventually becomes a rogue. The Autobots adjust to living with their new human allies, and Arcee deals with demons from her past regarding her fallen comrades. At the end of the season, the Autobots form an uneasy alliance with Megatron when Earth is threatened by the ancient and destructive being Unicron, who resides at the center of the Earth. Optimus Prime uses the power stored within the Matrix of Leadership to send Unicron back into hibernation, but the process erases Optimus' memory, which reverts to his original pre-war identity Orion Pax.