Go to Rookridge after purchasing or finding the rubber ball item and after defeating Dash. Stand in the center of the bridge facing the waterfall and throw the rubber ball as far as possible. If it lands in the waterfall slightly to the right, it will appear under the bridge out of view. Your dog will then become confused and will begin running in circles trying to get to it. To make your dog stop, punish or praise him. Note: Throwing another rubber ball will not work, as he will not see it.