The 26th episode of Transformers Prime aired on The Hub on the 15th October 2011 and was the final episode in the first season of the show.
The episode was also the final part of a three-parter and so opened with a round-up of the previous episode before Megatron is shown leading the Autobots further into the heart of Unicron as the title sequence rolls.
We return to the Autobot headquarters where Agent Fowler expresses his frustration of not being able to do anything. Ratchet explains that they simply must wait and see how the team of the Autobots and Megatron fair. He also makes mentioned that this is not the first time that Optimus Prime and Megatron have teamed up. This news shocks the Human characters and leads Ratchet to explain the origin of Optimus Prime to them. The story covers that time that Optimus, then Orion Pax, first meets the gladiator Megatronus who goes on to mentor the clerk. Megatronus wants to be named a Prime but when both the robots speak to the council it is not Megatronus who they are moved by but Orion. Megatronus becomes bitter and shorterns his name to Megatron before starting a revolution on Cybertron with his followers who he names Decepticons. The story goes that Megatron infects Cybertron leading Orion to travel to the planets core where he meets the spark of Primus. Primus sense the good in Orion and gifts his the Martix of Leadership and transforms him into the last Prime, Optimus Prime.
Meanwhile, deep inside Unicron, the Autobotsd and Megatron come under attack from what Prime describes as Unicron's anti-bodies. At this time Bulkhead starts to feel the effects of the Dark Energon on his systems.
Whilst all of this is taking place Airachnid, back onboard the Decepticon ship, has assembled the crew. She announces herself as the new leader and that the Decepticons should leave Earth and head for Regulon 4. Soundwave, who has been trying to contact Megatron silent disagrees leading the female triple changer to attack Megatron's 2nd-in-command. Soundwave defeats her with an ease not shown by any other Transformers in the whole series causing her to yield to him.
Back at the Autobot base Ratchet and the Humans are talk about how, with them being unableto lock onto the location of the Autobot's, are they suppose to be able to open a ground-bridge to their commrades when Ratchet notices Jack with a key. He questions the teenager about it who explains how its the key to the ground bridge and how Optimus gave it to him. Ratchet explains that he is mistaken, the ground-bridge has no such key and that what he is holding is actually the key to Vector Sigma!
Back inside the Earth's core, Megatron gets punished by Unicron in a homage to Galvatron in the 1986 Transformers: The Movie. Megatron manages to resist and, after savign Optimus unlocks the Spark Chamber of Unicrons and, along with Optimus, steps inside. After a few more quotes from the Generation One series, Optimus unleashed the power of the Matrix to defeat Unicon and bring the global distruptions to a hault but at a price. The Autobot leader not only uses the power of the Matrix but in doing so, causes himself to suffer from amnesia and so eh comes too thinking that he is still Orion Pax and that Megatron is still Megatronus and is his ally. At the same time the Decepticons, who can now lock onto Megatron, open a ground-bridge behind them. Realising this Megatron tells Prime that the Autobot's who have now arrived, as his sworn enemy, and ushers the Autobot leader through the ground-bridge back onboard the Decepticon ship leaving the Autobots confused.
Overall it was another fine episode, Starscream's lack of appearance though was a real shame, but the flash back to Optimus Prime's past and all of the other G1 references make this a fantastic end to the first series.