On their way to the Grand Festival at the Indigo Plateau, Ash & Co. come across a large group of Aipom, however the mischievous Aipom steal Ash's Hat and May's Ribbon Case and run off. However when they track down the Aipom, it turns out they worship a Giant Slaking who soon appears and kidnaps May. Can Ash & Co. rescue May from the Giant Slaking and get the Hat and Ribbon Case back in time for May to participate in the Grand Festival?