When Harold's failed attempt to steal the meteor lands it in Puplantis, it's up to "Charged Up" Zuma and Skye to get it back where it belongs before the superpowered pearls give away the secret of the Mer-pups.
It was another night with the Magic Mer-moon in the sky for the mer-pups to come out and play, Cap'n Turbot was carrying the Mighty Meteor safely in a crate on the Flounder, Rocky and Ryder were upgrading the meteor's security system. But, what Cap'n Turbot and Wally didn't notice is a robotic arm snatched the meteor into the water. Which he later found out.
Harold Humdinger was the one stole the meteor, he was going to use it to get his powers back and take over Adventure Bay. But, the meteor slipped away and landed in the magic shell of Puplantis, and with the power of the meteor and magic of the shell, it made the magic pearls bigger and more powerful, causing Puplantis to become extra magical. Harold discovered Puplantis, found the meteor, and got his powers back. He decided to become king of Puplantis as he started creating a throne, a crown, and a royal staff. Two mer-pups were terrified as they saw Harold in their home. They exited the castle for their safety.
Cap'n Turbot called Ryder about the problem and Ryder, Skye, and Zuma were on their way. Skye and Zuma charged each other up as they were heading into the bay. Zuma used his bubble shields around the vehicles and Ryder so they go underwater. When they made it to Puplantis, Ryder discovered Harold's vehicle, believing he's the one who stole the meteor. He told Zuma and Skye to keep the mer-pups safe, while he deals with Harold.
As Ryder entered the castle, a pillar crumbled and was about to crush Harold, but Ryder stopped it. Another pillar fell, Ryder calls for Zuma to come and help. Zuma entered the castle and pushed the pillars out of the way, saving Ryder and Harold. Ryder asked him to use his bubbles bring everybody and the meteor back up to the surface, and Zuma got the meteor out of the shell, making it turned back to normal. Then, everybody went back up to the surface. As everybody and the meteor are back out of the water, Skye used her whirlwind powers to lift the meteor back to the Lookout.
As the meteor was back in its security system, Cap'n Turbot called again, while he was at Puplantis underwater, saying the mer-pups thank the Mighty Pups for saving their home again. And Ryder said, "If a mighty meteor ever comes in your way again, just (mer-pup barking) for help."