S3·E13 The Visitor

While snowmobiling, two guys accidentally release an alien named Xylene from a strange container. At a park, Ben (as Wildmutt) steals Gwen's kite, so she casts a spell to make dogs attracted to him. Grandpa Max seems sad to be in St. Louis since it is where he met his wife. Xylene attacks, and Grandpa Max comes to defend, only to recognize her. Xylene reveals that she came to find the Omnitrix since she lost it when Vilgax attacked her ship. While Grandpa Max and Xylene talk about the past, a robot emerges from the area where Xylene was and attacks Ben and Gwen. The mechadroid attacks twice, taking Grandpa Max with him. Now Ben must work with Xylene (to his dismay) to save Grandpa Max.