City of Steel

Megatron transforms New York City into a Decepticon fortress called New Cybertron, and captures Optimus Prime.

Over New York City, Laserbeak flies into the Decepticons' underground base. The Constructicons are digging a hole in the ceiling and the Autobots don't have a clue. After hours of digging, the Constructicons manage to sink the Empire State Building underground.

The Autobots finally get wind of this and head to the city. Optimus Prime, Ironhide, Bumblebee and Ratchet plan to meet the rest of the Autobots at Central Park. However, Laserbeak spots them and reports back to Megatron. He plans to give the Autobots a surprising welcome.

At Central Park, the Autobots are ambushed by Soundwave and his crew, whilst underground the Constructicons inform Megatron that they're directly underneath Optimus Prime. Megatron orders them to dig while Optimus Prime is fighting Soundwave. Taken by surprise, Prime falls into the Decepticons' underground base where Megatron severs his motor relays, making him powerless. Megatron then threatens the remaining Autobots that unless they leave he will melt the Autobot leader down to scrap. He also shows them his master plan, which is to rebuild New York into New Cybertron. The Constructicons raise the Empire State building back up, but now it looks like a Cybertronian fortress. Forced to leave the city, the Autobots are gloomy until Spike comes up with a plan to get into the city undetected.

Seemingly victorious, Megatron gloats over Prime's still body. However, Megatron is still worried that Optimus Prime might try something and orders Hook to disassemble him, which he does with a handy energy blade. After Optimus is turned into a pile of parts, Megatron picks up his head and reactivates Optimus so he can gloat. Prime responds that even though he's in pieces he will still fight. Prime then activates his arms and trips up Megatron. Megatron orders the Constructicons to dispose of Prime's remaining parts how they choose, but he gets to keep the head.

Spike, Bumblebee, Ratchet, Hound and Mirage enter the City through the sewers in the hope of rescuing Prime undetected. Elsewhere, the Constructicons are very pleased with themselves for what they did with Prime's left over body parts. They have special plans for his right arm and weapon.

While scanning for Prime, Hound is confused because his scans show Prime was behind them when before he was ahead. Mirage then spots a giant robot alligator seeming to be made of Prime's body parts (dubbed the Alligaticon) and the Autobots run away. They trap it in a train and send it and the train packing. When they reach the underground base they find Prime's head and reattach his circuits so he can speak. Prime then activates his legs remotely to come to him and the rest of the Autobots figure out that the Alligaticon was made up of Prime's parts. After capturing it, Ratchet reassembles Prime, minus the right arm. Now that Optimus is safe, the Autobots attack. The Decepticons have turned half of New York City into New Cybertron, complete with killer taxis, and they're using Prime's arm as a weapon on top of their fortress. The taxis go for Bumblebee, Sideswipe, and Sunstreaker, but Prime runs them down.

After breaking through the Decepticon defenses, Optimus Prime, Ironhide and Ratchet plan to scale the fortress to reclaim Prime's arm. Bumblebee and Spike plan to help by distracting Megatron and Soundwave, even going so far as to insult Megatron. Megatron orders an air strike, but when Starscream is downed, the Constructicons become Devastator and he follows Prime's team up the building. Meanwhile, Spike and Bumblebee manage to sneak in and annoy Megatron, by calling him Megaklutz, and tricking him into destroying the device that controlled Prime's arm. Outside Devastator captures Prime and knocks Ironhide and Ratchet into the fortress. Wheeljack then comments that the whole thing reminds him of King Kong as he tries to assist with his remote controlled helicopters. Spike then informs Prime that his arm is no longer controlled by Megatron, and Prime takes the opportunity to use it against Devastator. After Devastator gets hit Prime falls but is saved by Ironhide and Ratchet and as usual the Decepticons retreat.

Now the city is saved, Prime is back together and Bumblebee got a souvenir (an 'I ❤ NY' bumper sticker). The Autobots roll out and return home.

—Long Haul, commenting on his alternate mode.

—Ratchet, trudging through the sewers of New York.

—Starscream agrees with one of Megatron's plans, which heralds the coming of the apocalypse.

—Optimus Prime, preparing to crush the battle taxis.

—Mix-Mix-Mixmaster!