After a battle with Dr. Animo in a power plant, Ben notices something strange is happening with the Omnitrix but doesn't tell anyone. Tetrax arrives and tells them the Omnitrix is broadcasting a self-destruct signal. Tetrax and Ben go to find the creator of the Omnitrix to fix it before it destroys itself and the universe along with it. Gwen stows away to help her cousin.

Ben Tennyson falls through a wormhole and encounters Rex. The two heroes must unite against a foe that can absorb their powers.

Based on the original animated series Ben 10. Ben becomes targeted by an evil Mechamorph Warrior, named "Retaliator," who mistakenly blames Ben for something he did not do and attempts to destroy all aliens.