After shrinking it, Bowser, King of Koopas, has his hands on the Mushroom Kingdom's castle and all of it's loyal toads. Bowser is keeping the castle hostage until Princess Peach, ruler of the Mushroom Kingdom willingly marries Bowser. Its up to Mario, Luigi, Princess Peach and the kingdom of Sarasaland's princess, Daisy, to steal the place and all of the toads back in a great heist.