While in a summer trip to a "resort" of their teacher's friend, the Megarangers find themselves in a ghost city. There is no one in the houses or in the whole island. Only a boy who witnessed his big sister kidnapping knows its related to a foam of a coral monster. They eventually get attacked by Coral Nezire who wants to transform humans into corals and fill the ocean with them in order to ruin the environment. Mega Blue was the only one who were not capture and is rescued by the boy. He said he saw all the monsters attack but didn't say a word because he wasn't prepared to hear the locals being judgmental about him not being brave to save his sister. Mega Blue incentives him to stand up and his help was crucial. Blue find the others and stop the mutation. The boy finds out his secret identity but the Megarangers found the weak point of the monster, so everything is OK again.