Greg accidentally leaves his rock at the museum. He and his friends go back to get it, only to discover all the magnetic rocks are gone. By night, they find that Luna Girl stole the rocks for her Luna magnet to pick up bigger things, like vehicles. She uses them to try and destroy things, including the PJ Masks. But instead of trying to get the mission done, Gekko tries to go after his rock, and that causes the heroes to struggle to get the mission to a success. His friends tell him that's it's not important like the mission is, and he sacrifices his rock to stop Luna Girl.