The episode starts off at night with Luna Girl and Motsuki flying around the town. Despite having a bit of a crash landing, the girls still manage to enjoy themselves and have fun. The two approach the museum, where flags about a new telescope are hung. Since Luna Girl had already attempted to steal the telescope, they decide to race around the building. Motsuki flies one way, and Luna Girl flies another way. Motsuki completes her lap and wins the race; however, Luna Girl has completely disappeared.
The next day, Connor, Amaya, and Greg walk over to the museum to see the giant, powerful telescope when they see one of the ripped telescope flags. Later that night, PJ Robot shows the PJ Masks through the PJ Picture Player an infuriated Motsuki, who had arrived at headquarters earlier, demanding for their help, but zapped the security camera when she received no response. She is now located at the museum, so the PJ Masks take the Owl-Glider and fly over to the location.
Motsuki is in front of the museum looking for Luna Girl. She happily turns around when she hears voices from behind, but turns sour again when it is only the PJ Masks arriving to help her, knowing that they took too long to respond. Nevertheless, she tells them that Luna Girl is gone, and despite being at odds with each other usually, they still find some ways to have fun with each other. The last time she saw her was by the museum. The PJ Masks believe that Luna Girl must have gone in to steal the telescope, but Motsuki denies this, saying that she does not want the object.
The PJ Masks tell Motsuki to follow them if she wants to find Luna Girl, advising her to stay calm. Suddenly, Motsuki finds Luna Girl’s Luna Board, which she never loses, and a pile of moon dust. She tells them to follow her, and takes off to find more moon dust piles. The moon dust piles lead to the end of the alleyway, where the Mystery Mountain portal is located. She turns around to notify the PJ Masks, but much to her annoyance, no one is there.
Night Ninja and his Ninjalinos suddenly appear next to Motsuki. They offer to help her find Luna Girl instead of the PJ Masks. At first, Motsuki is unsure, but when she uses her telepathic powers, she finds the team still by the museum, deciding to follow their own clues. She also hears them sharing their reluctance for her to follow them, stating that she can be a bit of baby. Infuriated by their comments, she agrees to let the ninjas help her. Night Ninja opens the portal to Mystery Mountain, saying that Luna Girl must have gone in there, and everyone goes in.
Inside the museum, the PJ Masks are in position, waiting for Luna Girl to sneak in and steal the telescope. They come out and fire their powered projectiles when they hear sounds, but no one is there, except for a pigeon that briefly flew inside for a moment before heading out. The PJ Masks head back to the Owl-Glider to track where Motsuki went. PJ Robot messages them, and reveals that she is with Night Ninja and the Ninjalinos at Mystery Mountain.
Halfway up the summit, Motsuki finds more moon dust, meaning that she must be closer to finding Luna Girl, according to Night Ninja. The Ninjalinos give her a pillow to rest on, and they make her more comfortable the rest of the trek up, Motsuki unaware that Night Ninja was the one who left the piles of moon dust. Meanwhile, the PJ Masks arrive at Mystery Mountain and catch up with the villains as they arrive at the peak. Catboy pulls the Ninjalinos away from Motsuki, and the PJ Masks prepare to confront the ninjas. Motsuki stops them, though, saying that they are helping and listening to her, unlike the team, who has called her a baby earlier.
The PJ Masks watch as Motsuki and the ninjas enter through the gates. After hearing what she said, they doubt that she is going to listen to them as they ignored her earlier. However, they still feel that something bad is going to happen. An Yu confirms this as she approaches the team and the Ninjalinos close the gates, throwing Sticky Splats at them. The four heroes barely escape the projectiles, but the pagoda is in danger.
The villains soon arrive at the building, where Motsuki hears some moth sounds. She looks over to see the moths trapped in a cage. Night Ninja reveals that he was the one responsible for everything; he was the one who captured Luna Girl and her moths last night. Two of the Ninjalinos bring Luna Girl out, who is stuck in a Sticky Splat boulder, while the other two jump behind Motsuki and sticky splat her to it. Angered that Night Ninja tricked her, Motsuki attempts to zap him, but with Luna Girl’s Luna Magnet in his hands, he drains the power from her crystal. With both powers combined, he is going to open the doors to the pagoda and make it into his new headquarters.
Night Ninja’s attention is grabbed when the PJ Masks and An Yu jump over the pagoda gates, intent on stopping him. He fires the Luna Magnet at the heroes, but fails to stop them, so the Ninjalinos throw Sticky Splats at them instead, sticking them to one of the dragon statues. With everyone out of the way, Night Ninja resumes to open the pagoda doors using the power collected in the Luna Magnet. The power suddenly fizzles out, so the Ninjalinos fan the Luna Magnet to quickly cool it down.
The PJ Masks apologize to Motsuki about not listening to her earlier and calling her a baby. She just got mad because she was really worried about Luna Girl, and they should not have ignored her just because she felt angry. Motsuki apologizes as well, as she just wanted to find Luna Girl so bad. Suddenly, everyone notices Motsuki’s crystal glowing. She explains that when she has big feelings, it glows, but since Night Ninja took her power away, it barely glows. Despite that, they see that her feelings have great energy, so they ask her to share her feelings.
Motsuki complies, and she shares her feelings about the course of what happened. She expresses sadness about losing Luna Girl, and she expresses anger about Night Ninja taking her. As her feelings grow stronger, her crystal glows stronger. Soon enough, the crystal gains enough power from Motsuki’s strong feelings, and the heroes are freed. Gekko then breaks the Sticky Splat boulder, and Luna Girl and Motsuki are also freed.
Night Ninja prepares to open the pagoda doors again, until they see the heroes freed from their prisons. As the Ninjalinos escape, Owlette blows the Luna Magnet out of Night Ninja’s hands. Luna Girl retrieves it, and after transferring Motsuki’s power back to her crystal, she zaps Night Ninja and throws him out of the pagoda gates. The Ninjalinos safely catch him, and as the ninjas run down the mountain, everyone shouts out the signature victory phrase, ending the episode.
Listen to those who need help, no matter how mad they are.
Love is a strong power, no matter who takes it away.
Emotions have great energy.
This is the twenty third episode to focus on a villain.
This is the first time Luna Girl and Motsuki are on Mystery Mountain.
They are also the sixth and seventh villains to visit Mystery Mountain.
This is the eighth time An Yu joins in the PJ Masks' victory chant.
Catboy gives Gekko a piggy back ride for the fourth time.
The scene where the PJ Masks are all on the museum might be a reference to the scene in Disney's 2014's Big Hero 6 where the team started using all of their powers thinking it was a villain and it turned out to just be a bird.