The luxury liner to Slateport City, where the Pokémon Contest Grand Festival will be held, has barely lifted anchor when Ash and friends learn that a famous master thief is believed to have snuck on board the ship.  Sure enough, in only a matter of hours, the Ribbon Cup—the prize to be presented to the Festival’s winner—disappears. Knowing this could spell disaster for the Festival, our heroes work with Officer Jenny in a sting operation designed to draw out the thief, a master of disguise capable of assuming any identity he chooses.