When Gwen is abducted, Ben as XLR8 follows her abductor to the future where they discovered that her abductor is the future Gwen and they discover his future version of Ben and Grandpa Max. In the future, Dr. Animo revives Vilgax and plots to open the Null Void chamber. Both Bens must work together to stop them.

Dressed as Pilgrims, to honor their history, while in the streets of Salem, MA, Ben, Gwen, and Grandpa Max witness an explosion of a nearby building. But when Ben rushes to the rescue, Charmcaster is there waiting with a spell to take over Ben's body and the Omnitrix. Only things go awry and Gwen and Charmcaster switch bodies. Gwen goes to prison and the sorceress is brewing a plan to gain the Omnitrix. Now Gwen must find the way to get out of prison, alert her family against Charmcaster, and get her own body back using every trick up her sleeve... or Charmcaster's.