Grace O'Malley (the famous Irish pirate queen) has hidden her treasure at the end of a rainbow but a great storm has broken the rainbow into its 7 pieces and is now scattered around the world. Grace, her pirate crew and their parrot set sail on a great voyage to find the rainbow colours and fit them back together so that it will lead them to their hidden treasure. But they face challenges and adversities on their voyage to reclaim the treasure as the colours of the rainbow have fallen into the hands and paws of others who do not want to hand them over. Can Grace and her pirate crew succeed on their mission or will they be treasureless pirates forever?!