The last time they fought the Decepticons, they didn't have Devastator on their side, but now the Autobots lost and their leader, captured. What will the Autobots do?
Meanwhile, on the Nemesis, Megatron discusses his plans for the Allspark, then, he plans to remake Cybertron in his own image, but first, he must put Optimus Prime out of his misery.
Then, the Autobots and Humans meet Sideswipe, Sunstreaker, Trailbreaker, Grapple, Hoist, and Cliffjumper. Now, they must plan a raid to rescue Optimus, and stop Megatron, once and for all! And, as for how to catch the Nemesis, enter Agent Simmons of Sector Seven.
Simmons: "After this is over, you and your families will receive protection by me."
Steven: "Now, that's wicked!"
Carly: "You sure about this, Witwicky?"
Steven: "It's either Optimus or nothing; we gotta try."
Now, the Autobot-Human Alliance must go to great lengths to save Optimus from the Decepticons and destroy the Space Bridge.
But first, they must face Devastator!
Chelsea: "Look out, Jack! Devastator at 12:00!"
Wheeljack: "Got it!"
[...]
Grapple: "This is so cool!"
Hoist: "I know, right?"
The Autobots are holding their own against Devastator, but Starscream gets in the way.
Starscream: "You won't get in Megatron's way!"
Steven: "We'll see about that! Hey, Bee! Wanna hitch a ride?"
Then, Bee and Steven ride Starscream straight to the Nemesis, where he crashes into Megatron, saving Optimus.
Optimus: "As usual, you're just as stubborn as I was, Steven, Bumblebee."
Steven: "Glad we can help."
At this point, Megatron is so pissed-off that he blasts Optimus, but the Allspark appears in Bumblebee's hands, shielding them from his attack while restoring his voice.
Bee: "Whoa. Wicked!"
Steven: "Bee? Is that you?"
Bee: "It's me, Steven. I'm back!"
Steven: "Wicked!"
Now, it's Optimus against Megatron, but the Space Bridge activates.
Megatron: "You're too late, Prime! Too late! First, Cybertron, then, the world! What can you hope to stop me?"
Prime: "It's obvious: we light our Darkest Hour!"
Meanwhile, the Autobots defeat Devastator while Optimus fights Megatron for the fate of California, and the Earth.
Then, Optimus destroys the Space Bridge. However, the Space Bridge appears to be unstable, so Optimus tries to stabilize it with the Allspark. But that opened the way to new worlds, and the Space Bridge disappeared along with the Allspark.
Luckily, Optimus, Bee, and Steven made it out alive and the Earth is saved.
After the battle, it's Summer Vacation time with the Autobot-Human Alliance! So that means...
It's DJ Chaser on the turntables once again!
Chelsea: "What's up, California! It's yo girl, DJ Chaser, and this time, she ain't alone!"
Kicker: "There's a new DJ in California, and his name is DJ Kicker!"
Now, Steven, Carly, and Chip live it up with their Summer Vacation.
Trio: "Summer Vacay! Wicked!"
As for Megatron, and the Decepticons, where are they?