This episode article is in need of a synopsis. A synopsis is intended to be a very detailed description of what occurs in the episode.
The PJ Masks are driving in the forest of Mystery Mountain on their PJ Rovers. As they praise their vehicles, they unknowingly drive past Night Ninja and his Ninjalinos, who are hiding in the bamboo stalks. Hearing their compliments, Night Ninja decides to have one for himself, and orders his Ninjalinos to sticky-splat them. The Sticky Splats are thrown, but the PJ Masks dodge them, and a chase begins.
After the chase, the Ninjalinos are sticky-splatted, and the PJ Masks have stopped for a break, congratulating each other on a job well done of driving. The celebration is short-lived, however, when Night Ninja sneaks up to the PJ Rovers and takes off to the mountain with Owlette's rover. Catboy and Gekko go after the villain in their vehicles, while Owlette flies overhead to guide them on where he is going. Fortunately for them, halfway up the mountain, Owlette's PJ Rover automatically stops, and the team catches up with Night Ninja. Owlette gets back on her vehicle, and the PJ Masks ride back down the mountain.
This is the fourteenth appearance of Mystery Mountain.