Way Big grabs him, but Azmuth attacks Way Big. Max tells Carl that he'll find him. Later, Ben gives his report on the Age of Exploration as Tetrax leaves Earth. Retaliator asks Heatblast where to find the To'kustar. Gwen falls, but lands safely as Retaliator and Evil Way Big fight. Retaliator keeps demanding an alien and Four Arms knocks him away, but he teleports back and attacks Four Arms.
Ben states that he is supposed to go fishing with Grandpa Max, but his parents stick to the punishment. The To'kustar from earlier appears and walks away. Later Ben is riding on his through a green colored Bellwood, which he finds abandoned. Unfortunately, the Omnitrix malfunctions again and transforms Ben's parents into Wildmutt and Heatblast, causing Gwen to realize that the evil Waybig is Azmuth, himself. Afterwards, Ben calls Max in the hopes that he's needed to save the Earth and reveals he wishes he was still on summer break fighting aliens around the country, but Max won't help him as he doesn't want Ben to push away his family like he almost had with Ben's father when Max was still fully active as a Plumber. Plot: Taking place shortly after the events of the original Ben 10, Ben, Gwen and Grandpa Max spend their evenings fighting aliens on the streets of Bellwood.
Retaliator chases him and shoots Stinkfly, which knocks him out of the sky. Ben grabs onto the fin and the Omnitrix flashes, causing the To'kustar to then disappear. Tetrax recognizes the To'kustar, but Retaliator arrives into the ship and aims a gun at the three. Leaving Grandpa Max and Tetrax to handle the parents, Ben and Gwen follow Azmuth's father and the evil Waybig to the park where Ben transforms into Waybig to subdue Azmuth while he and Gwen try to reverse the transformation. Meanwhile, in the Rust Bucket, Gwen tries and fails to track Ben, only getting as far as the forest.
Evil Way Big realizes who he and Retaliator are and Retaliator does as well. Before he can explain this new ability, the ship is attacked and Ben is sucked out into the atmosphere, falling to the ground as Diamondhead. Suddenly, a crystal flies through the window and arrives. Tetrax decides to take Ben to meet Azmuth and activates a new function on the Omnitrix. Retaliator frees himself and attacks Azmuth.
This is not the first time where some super powered alien comes after Ben for reasons unknown. On the road, the Omnitrix makes a bright flash. They go in search of him, only to find Tetrax and discover that Azmuth's ship earlier disguised as a semi truck has crashed and was destroyed by the evil Waybig. Azmuth says that the Omnitrix was overloaded with mana, confusing Gwen, who was ignorant at the time about her lineage, and that he came to Earth to fix the Omnitrix, but was transformed into an Evil Way Big. Ben tries to transform into Way Big, but he transforms into Stinkfly instead.
They walk off, but Azmuth puts on the Mechamorph armor and merges with the Rust Bucket in order to repair it. Azmuth reprimands Ben and Gwen for their errors and reveals his father is a Grey Matter wielding a Mechamorph-type armor. He stumbles across a figure at a dark corner who he believes to be Max until it ignites and is revealed to be Heatblast who attacks him but, but he escapes, only to then be attacked by , , , , and Upgrade. Upgrade comes out of the pieces and reforms but is jolted by the spell before suddenly reverting back to Ben. Suddenly, Ben and Retaliator are then attacked by a swarm of. Gwen shields herself as the To'kustars fight and Way Big knocks out Azmuth, but Retaliator sees him and attacks.
Meanwhile, Gwen and Grandpa Max receive a call from Ben's parents Carl and Sandra informing them that Ben has escaped the house. Ben realizes that she is right and Tetrax tells Ben and Gwen to stop Azmuth and Retaliator. And please never make a hit and run away. Retaliator apologizes and Azmuth apologizes as well and says that his Mechamorph armor causes aggression. When the teacher grabs Ben's planner and looks through it, he finds an unflattering picture of himself in it he gives Ben detention. During a battle against a robotic tank, Ben as Upgrade and Gwen argue about the best way to defeat it, leading to Gwen using a dismantling spell on the tank while Ben is attached.
They go to meet Azmuth but are attacked by an evil version of Waybig. Azmuth starts to go home, but Ben asks him to transform his parents back into normal. There is no shortage of that going on in this movie. The show keeps the viewers asking questions until the last moment: Where is Azmuth, who is the mysterious attacker, what is wrong with the omnitrix etc. Azmuth reprimands Ben and Gwen for their errors and releases his father from the Mechamorph armor.