Ben's trip to Portland with his family is interrupted by the arrival of a brand new, eleventh alien, Gax, as he fights another one of Dr. Animo's monsters. But when the Omnitrix starts behaving strangely, Ben begins to transform from one alien to another without being able to stop.

Ben heads far into the forest to prevent his unpredictable transformations from causing damage.Meanwhile, Vilgax, who seems to be the same species as Gax, lands nearby.The latter helps Ben discover his powers,but he quickly realizes that this new friend is in fact an opponent.