Episode 18 of Transformers Animated first aired in Canada on YTV on the 19th April 2008, a week before the USA. The episode was titled The Return of Headmaster and continued straight from where episode 17 left off, with Porter C Powell in charge of Sumdac Systems.

Episode Summary
The episode starts with Sari Sumdac complaining about how she has been evicted from her home by Porter C Powell, the new CEO of Sumdac Systems. To her horror she is introduced to the new head of Sumdac Systems, Henry Masterson aka Headmaster. The scene jumps to Detroit, where Sentinel Prime and Optimus Prime are giving a speech. This is mainly used to show Sentinel's disgust of organics and his lack of respect for Optimus Prime. Whilst this is going on Sari moves in with the Autobots, and Bulkhead and Bumblebee try their hardest to make her feel at home.

At the same time Porter C Powell tells Henry Masterson that he wants Sumdac Systems to start developing robotic weapons, to make profit, to which Masterson decides that Sentinel Prime would make the perfect test subject. He phones Captain Fanzone, making a crank call, pretending that he has spotted the Decepticons in Old Detroit. Hearing this, the two Prime's go to investigate, with Sentinel leaving a trail of destruction in his wake. When they arrive the pair split up and it's not long till Sentinel finds Headmaster .. well actually it's the other way around. A few seconds later and Sentinel Prime is left without a body.

Optimus find's sentinel and the pair head to Sumdac Towers to find Porter C Powell and Headmaster. Meanwhile Bulkhead and Bumblebee continue to fail to make Sari feel better. Optimus is forced to leave Sumdac Towers by Porter C Powell, but tracks down Headmaster (who is at a port). He is then attacked by Sparkplug (Sari's dog) and her teacher-bot, who are now under the control of Headmaster. Still carrying Sentinel Prime's head, Optimus defeats teh pair of robtos and makes it on-board Headmasters boat.

Once on-board a fight soon starts between Optimus Prime and Headmaster, now using Sentinel Prime's body. Optimus manageds to defeat Headmaster-Sentinel, ripping off his arm and cutting off the Headmaster unit (quiet easily compaired to their previous encounter). Headmaster transforms and prepares to escape, as he did before, but Optimus kick's Sentinels head at thim, knocking Headmaster to the ground.

When Fanzone arrives to arrest Henry Masterson, Port C Powell turns up and explains that Henry has done nothing illegal, so the pair walk free.

The scene jumps again to the Autobot base, where Prowl tells Bulkhead and Bumblebee to listen to Sari, rather than guessing what she wants. The scene jumps for a second time to Ultra Magnus' ship, where Optimus covers for Sentinel, who appologises to the former maintenance-bot, much to his distaste.