During the war on Cybertron, the Mini-Cons, mini-transformers who can be used as upgrades by their bigger brethren, crash lands on Earth. In present day, a group of children finds their ship by accident which brings the war to Earth.
Escaping from the confrontation between Bots and Cons, Alex, Rad and Carlos find the cargo hold of the Exodus underground and are adopted by three minicons. Retreating to the moon, the 'Cons make the wreck of the Exodus there their base.
Alexis, Rad and Carlos introduce themselves to Optimus Prime, Hot Rod and First Aid, and get a condensed history of the conflict. Meanwhile, on the moon, Megatron plots to capture the minicons that are now appearing all over earth.
The children join the Autobot team and head out on their first mission to find a newly waking minicon. The Decepticons arrive to combat them. Optimus Prime finds his old minicon partner.
The newest minicon activates in the middle of a forest: both sides fight for it, and the conflict sets the trees alight. The Autobots attempt to battle the blaze, while Starscream finally acquires his own minicon.
Rad and Carlos smuggle their minicons out of the base to visit the town's carnival. Billy and Fred see them transform and try to capture one, but are thwarted by Hot Shot.
The Decepticons capture all the children to use as hostages in exchange for the Autobots's minicons. Fred and Billy are officially introduced to the Autobots.
The latest minicon re-activates in the subway system of a large city, and there's the usual scramble to see which side can get to it first. And a new transformer makes himself known - but which side is he on?
From an ancient submerged city a beautiful girl issues a warning about the devastating power - and danger - of three special, combining minicons. The Autobots already have two of them: now Megatron aims to capture the third.
The children learn more about the history of the minicons and the war. The latest minicon alert leads the team to a volcanic island: the volcano erupts in the middle of the usual 'Bot vs 'Con battle.
The Decepticons gain access to the Autobot base, and attempt to take the other two minicons that, with the one Megatron captured on the island, combine to make the supremely powerful Star Sabre. Can Hot Shot save the day?
Hot Shot proves himself very skilled with the Star Sabre, but the arrival of a new Decepticon proves him overconfident. The Decepticons acquire the first of another three combining minicons which transform into the ultimate form of defence.
A new minicon activates inside a highway tunnel, and the race is on to see who reach it first. Hot Shot is becoming more proficient with the Star Sabre. A new transformer arrives, claiming to be an Autobot, but Rad has his doubts.
Grabbing onto Megatron at the end of a battle, Hot Shot and Sideways are transported to the moon. The battle resumes, but Hot Shot is betrayed, and Starscream gains the Star Sabre.
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?
Autobot Blurr joins the team, but proves himself not much of a team player. The Decepticons acquire the final minicon to create the Skyboom Shield, the most powerful defensive weapon in the universe.
Confident of his ability to finally overcome the Autobots, Megatron challenges Optimus to battle. However, when all seems lost Optimus' minicon summons the Skyboom Shield to protect his master.
The Decepticons lose another battle: Megatron takes out his frustration on Starscream, beating him half to death for no reason. Sideways uses the situation to try to foment unrest and rebellion.
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?
A new transformer enters the solar system. On the moon, Thrust the master tactician arrives to assist Megatron in his battle against the Autobots, but all does not go according to plan.
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.
With Starscream's help, the Autobots infiltrate the Decepticon moon base, attempting to rescue all the minicons Megatron has captured and forced into building a spaceship.
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.
As the Axalon chases the Decepticon ship, hundreds of minicons appear. The 'Cons turn back to fight, and the 'Bots seem doomed, but the minicons resurrect Optimus.
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.
While the battle continues, Hot Shot goes to Cybertron to try to convince Galvatron of the impending danger. Thrust's true allegiance and agenda is revealed.
Thrust flees into the depths of Cybertron, pursued by Hot Shot and Wheeljack - and, separately, Starscream, who saves the children from being killed. The children discover the origins of the minicons.
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.
The only way to defeat Unicron is to wake the minicons inside him and attack from within as well as without. Red Alert and the kids use the portal to travel to Unicron's core.
