When Ben wakes up one morning, he finds the Omnitrix missing from his arm. Weirder still is the fact that Gwen and Grandpa Max have no idea what he’s talking about when he asks about it. Ben soon discovers that he’s actually reliving the very first day of summer, the same day that Ben found the Omnitrix to begin with, but in an alternate reality. At the campsite, Ben tries to find the Omnitrix as it crashes to Earth, only to find out that it has already been found by Gwen. Gwen quickly adjusts to the Omnitrix’s powers, with much greater ease than Ben. But Gwen uses the Omnitrix much more than required, hence when actual need for Omnitrix is required, i.e., when Vilgax attacks she finds the Omnitrix is discharged and will take some time before it becomes usable. Also, unlike the first episode Vilgax was not injured at all earlier and is already heading for Earth to take it back from her, preferably in a very painful way. Ben’s going to have to prove himself to be a hero without the Omnitrix to back him up if he wants to save Gwen and give her advice on which alien to use in which situation as she finds herself at loss in that department, then as she gets captured by Vilgax and then rescued by Ben and Max, the Omnitrix flies off of Gwen and lands on Max, granting him the Omnitrix’s tremendous energy and power witch leads to ben getting upset. Aliens transformed into: Heatblast (Gwen), Grey Matter (Gwen), Diamondhead (Gwen), Fourarms (Gwen), Upgrade (Max).
Note: This is a non-canon episode that is said to have taken place in a parallel world and alternate universe.