With the loss of the Star Sabre, the Autobots keep losing battles. In a fog-bound valley, Megatron plots to get the Sabre from Starscream, at the same time boosting his crew's confidence in himself. Scavenger's secret is revealed.
The Autobots and Decepticons face off amongst snowy mountains in the battle for the latest minicon. Despite using the Star Sabre, this time Megatron loses - and Scavenger finally gains the Autobots' trust.
A weekend's camping trip to the valley below the dam goes wrong when a violent storm moves in. With Red Alert trapped in a mudslide, the sluice gates about to open, and local reporter Kelly filming, how will the Autobots escape detection?
Trapped in cyberspace with Sideways, Alexis, Rad, Carlos and their minicons become aware of a massive evil entity, far more powerful and dangerous than Megatron, lurking threateningly in the background. Or was it all a dream?
With Optimus damaged and temporarily out of commission, the newly-arrived Jetfire takes command - and seriously underestimates the Decepticons. But on the verge of defeat, Optimus reveals a new ability.
On the moon, Thrust continues his plotting with Megatron. On earth, despite Jetfire saying he's one of the good guys, the kids are suspicious of Sideways - as are the Decepticons. And something huge and ominous is approaching earth.
The massive Tidalwave joins the Decepticons, but is, seemingly, defeated in battle by Hot Shot and Blurr. Alexis discovers three new minicons, which Sideways says combine to create another ultimate weapon, the Requiem Blaster.
The kids try to gather the three Requiem Blaster minicons together. Sky Blast at first resists, then sings the others to him to save Optimus. They all realise there's more to the minicons than first appears.
Understanding that the minicons want to be in charge of their own destinies, the kids sneak the new team out of the base. Thrust finds them, but so do the Autobots who save the day. It's agreed the minicons should not be forced to fight.
Enthusiastic young Sideswipe, Blurr's hero-worshipper, joins the team and Optimus tasks Hot Shot with training him. Wheeljack also arrives on earth, bent on revenge for Hot Shot seemingly abandoning him during a battle on Cybertron.
Desperate to make amends to his old friend, Hot Shot allows Wheeljack to shoot him, but this isn't enough. Wheeljack takes Sideswipe hostage, but Hot Shot rescues him. On the moon, Megatron welcomes Wheeljack to the Decepticons.
Megatron sacrifices Starscream, leaving him to face the Autobots alone while the Decepticons infiltrate the Autobot base to capture the Requiem Blaster. Smokescreen sacrifices himself to try to protect the Blaster minicons.
Hearing Megatron say he is nothing more than disposable cannon fodder, Starscream defects with the Star Sabre. To prove he's genuine, he gives the Autobots details of the moon base. Red Alert works on what's left of Smokescreen.
Alexis tracks a minicon in the vicinity of Mars. Starscream gets there first, but is disabled by Tidalwave. Jetfire rescues him: on the way back Starscream spots and tries to entice the minicon. But first they must get past Megatron.
With the kids befriending and welcoming him, the Autobots deeply suspicious of him, and driven by his need to kill Megatron, the deeply conflicted Starscream trusts Thrust and returns to the moon base with the Star Sabre and Skyboom Shield.
Sabre, Shield and Blaster together create the Hydra Cannon. Installed on their new ship, the Decepticons test it on a comet - then Megatron orders Starscream to use it to destroy the Autobot base. Problem is, that'll also destroy the earth.
Optimus and Jetfire attack the ship, but can't stop the Hydra Cannon being deployed. Optimus makes the ultimate sacrifice and takes the full blast. Afterwards only his minicon and his matrix are found, but at least earth survives.
Hot Shot insists they should take vengeance on the Decepticons: Scavenger, with the support of the minicons, reminds him of their true purpose. With Hot Shot's realisation of the right way forward, Jetfire hands over command to him.
With the Autobot ship ready to leave, Hot Shot, supported by the rest of the team, refuse to let the children accompany them. But then the minicons refuse to allow the ship to depart unless the kids are on board.
Hot Shot and Red Alert are sucked through a wormhole. The minicons guide the Axalon to their location, where they are all attacked by Nemesis Prime. As the planet breaks up, the 'Cons shoot down the Axalon and escape.
The 'Bots reach Cybertron to find Megatron (now calling himself Galvatron) already winning the war. The minicons fend off an attack by Unicron, warning of great danger, but Galvatron believes it just an Autobot trick.
Thrust joins Sideways by passing through a portal deep underground: his pursuers follow and find themselves on Cybertron's moon, which begins to disintegrate. To everyone's horror, Unicron is revealed.
With the minicons protecting Cybertron and Hot Shot's team attacking Unicron from outside, and Optimus and Galvatron facing Sideways at Unicron's heart, the purpose and meaning behind the endless war is revealed.
With Unicron seemingly defeated, Galvatron insists on settling things with Optimus, and the fight wakes Unicron again. Galvatron makes the ultimate sacrifice to finally end the threat. Jetfire and Hot Shot return the children to earth.