The episode starts off with Connor, Amaya, and Greg running upstairs to the library portion of the museum to take a look at an exclusive Master Fang comic that contains a secret on how to achieve true greatness. Connor plans to use his library card to borrow the comic and find out what it is when the Teacher announces that someone has stolen the comic. That night, the PJ Masks take a look at the PJ Picture Player and see Ninjalinos entering the museum.
The PJ Masks arrive at the museum in the Cat-Car. They sneak quietly around the building, looking for any signs of Ninjalinos, but there is only a puddle of glue on the floor. In addition, a footprint is left behind, which belongs to Armadylan. He is in the museum reading Master Fang’s comic. He promises to put it back once he finds out for himself the secret to true greatness; then he can become the greatest hero ever.
Gekko suggests to put the comic back where it belongs, but Catboy wants to figure out the secret as well, saying that Armadylan has not properly taken the comic out yet with a library card. Armadylan does not care about the library rules, though, and they fight over the comic. They collapse, and the comic opens up to the page where Master Fang shares his secret. It says that to achieve true greatness, they must go to the sports hall. Feeling that it must be a clue, Catboy and Armadylan race to the building, with Owlette and Gekko running after them. None of the heroes are aware that Night Ninja and his Ninjalinos were in the museum all along.
The four heroes reach the sports hall, but the doors are locked. However, Catboy runs around and finds a picture of Master Fang on the wall. It is freshly painted, though. The next clue in the comic reads that the secret is a blast from the past. Armadylan knocks the wall down, and he runs through, Catboy running after him. While the two boys resume fighting over the comic and arguing whether speed and movement or strength and power are the key to true greatness, PJ Robot contacts the PJ Masks and shares his suspicions about the clues that were recently found. Owlette and Gekko agree and suggest that he should join them to help them figure out what is really going on.
PJ Robot drives into town in the PJ Seeker. He analyzes on the computer for any clues on the ongoing situation. Meanwhile, Catboy and Armadylan walk around and stop in the middle of the town to read the last clue written in the comic. They are near true greatness; all they need to do is walk in the direction that they are supposed to go in with their eyes closed. Keeping their hands in front of them, they walk to the end of the alleyway where they feel what is apparently a mystical wind and something cool, wet, and smells like cranberry juice. It is actually the Ninjalinos creating the mystical wind with the fans and the puddle with one of the Ninjalinos’ spilled drink.
Night Ninja appears and sticky splats Catboy and Armadylan. He reveals that he made up all the clues to find Master Fang’s secret in order to get rid of all the heroes in one night. Starting with the two boys, he uses the ninja travel spell written in one of the scrolls to transport them away to the Mystery Mountain cell in the cave. He and his Ninjalinos then hide when they hear Owlette and Gekko in the distance, looking for their friends. As they find the comic book on the streets while PJ Robot approaches them and explains that Night Ninja is the one responsible for this, the villain uses this chance to trap the three remaining heroes in a Sticky Splat web.
Catboy and Armadylan are ashamed of what happened. Because of their obsession and competition with finding true greatness, they fell for Night Ninja’s plan. They need to go back to the city to help the others, but if they are to do that, they need to work together to escape their prison. Finding a hollow portion behind the wall, the boys use their powers together to break it down. They go out through one of the traps leading to the pagoda where An Yu is meditating, and once they exit the gates, they use their powers to quickly roll down the mountain.
Back in the city, the Ninjalinos try using the ninja travel spell on Owlette, Gekko, and PJ Robot to transport them to the prison cells, but fail as three of the Ninjalinos are transported there instead. Night Ninja prepares to do it himself since it does not work in the group’s language, until Catboy and Armadylan exit through the Mystery Mountain portal and frees the three heroes from the web. All the heroes now freed, Night Ninja and the remaining Ninjalinos escape as the villain vows to return.
As for Master Fang’s secret, PJ Robot takes out the ninjas’ taped drawing from the last page of the comic. To achieve true greatness, all everyone needs to do is to share with their friends. Satisfied with the secret, Catboy and Armadylan agree to return the comic back where it belongs so that everyone can read it. All they need to do is sign it out. Catboy lets Armadylan use his library card whenever he needs to, and he accepts.
Arguing and fighting makes things worse (work together).
Being overly competitive makes things worse.
Don't be fooled by something you love.
Connor reveals to have his own library card.
When escaping their prison, Armadylan and Catboy go through the trap doors of the pagoda like PJ Robot did in "The Mountain Prisoner."
Night Ninja says that there is a language for his Ninjalinos called Ninjalino-ese.