Grandpa Max takes the kids to the music festival at Chicago, to watch his favorite band, Shag Carpeting. Ben did not care much about their presence there, as he's more worried about visiting a Sumo Slammer convention. As Ben and Gwen wander around, they find a weather man, Vance Vetteroy, with his weather robot, S.A.M. Vance decides to launch the robot to the sky to produce artificial rain, but a lighting strikes S.A.M., causing it to create a large, water-like creature that creates havok in the festival. Though the weather seems to be of little importance, now it is probably a good time for the Tennysons to make an exception.
