Connor and Amaya are planning for sports day at school, and Greg believes that working out will help make him stronger. But all the sports equipment has been taken, and no one is able to practice. The PJ Masks discover that Night Ninja is using the stolen equipment to strengthen up his Ninjalinos. Now they must reclaim what was stolen -- for the sake of sports day.
Today is Sports Day at the park, and Connor and Amaya are getting ready to leave once they finish preparing their bikes. Suddenly, they hear strange and loud sounds, which are coming from the shed at Greg's House. The two run towards it, and taking precaution, Connor slowly grabs the doorknob and opens the door. Out comes Greg, who falls down, and explains that he was trying to push open the door very hard. Connor and Amaya help him up, glad that they could help Greg out, and explain that he is much stronger at night when he is his alter-ego, Gekko. Greg agrees, and adds on that since that is the case, he would not need help from anyone. Now that he is out of the shed, he can grab his bike, and the three can head over to the park for Sports Day.
In the park, as Connor and Amaya place their bikes with the others, Greg is excited that with enough exercise from Sports Day, he can become strong in the daytime in no time at all. He then tries to lift his bike, but he ends up struggling and throws his bike into the other bikes, making them all fall down. Except for Connor and Amaya, nobody notices this, however, because Sports Day has been cancelled. All the sports equipment that were placed have disappeared. Wondering where everything has gone, the three decide to find it.
After the transformation sequence and the transport to headquarters, the PJ Masks check the PJ Picture Player for any information about the stolen sports equipment. They find out that it has been stored in the shed before Sports Day, but it has now been stolen. Wondering who has it, Gekko becomes determined to get it back, and prepares to show them that he is very strong, which confuses both Catboy and Owlette. Despite this, Gekko declares to take the Gekko-mobile and presses the Gekko Symbol icon on the PJ Picture Player screen. The PJ Masks take their respective elevators down to Gekko's base room, hop in the Gekko-mobile, and drive off into the water and out into the town.
As Gekko excitedly gets ready to face off with whoever stole the sports gear, Catboy uses his Super Cat Ears to hear any signs of that person. Soon enough, he hears some various singing voices, and points at the direction of where they are coming from. Gekko drives over to the park, and the PJ Masks jump out of the vehicle. Now closer to the sounds, they recognize the sounds of the voices and go into the forest. There, they spot Night Ninja, who is sitting down and reading, and the Ninjalinos, who have all of the sports equipment. They go up to him and demand that he give everything back, especially since the daytime kids need it. Night Ninja refuses, because he needs it for his Ninjalinos, or in this case, Super Ninjalinos. With the equipment, they can become stronger and stronger with each training, and in no time, they will be strong enough to learn his own ninja moves. The PJ Masks are not letting this happen, and start to go over to the Ninjalinos to retrieve the sports equipment. However, Gekko stops them, saying that he can handle this situation by himself, and walks over to them.
Approaching towards one of the Ninjalinos, who is lifting a couple of bicycles, Gekko takes one bicycle from him and walks away. He does not get too far, though, because a couple of Ninjalinos run towards him. They grab the bike, lift it along with Gekko, and throw him off. A couple more Ninjalinos join them, and with the balls in their hands, they throw it at him. Gekko gets out of the way, but he slips on one of the balls and crashes into Catboy and Owlette. The PJ Masks are surprised at what just happened: the Ninjalinos have gotten stronger. With this visual, this means that they are almost ready to train with Night Ninja. Night Ninja commands them to go to the next training spot, and they march over, grabbing the sports equipment and carrying him. Catboy commends Gekko for trying to get the sports gear back by himself, but explains to him that they need a plan that involves the whole team to retrieve the gear. Gekko refuses, though, because he claims that the Ninjalinos are small, which means he has to be stronger than them. He then runs off, while Catboy and Owlette look at each other, but run off with him as well.
With one switch of Gekko's gekko symbol, the PJ Masks are building a trap. However, it is mostly Gekko who is doing the work. The reason why is that although Catboy and Owlette are trying to either get the supplies needed or build the walls for their trap, Gekko quickly comes along and does it for them, much to their confusion. After a few moments, the trap is complete. Once the Ninjalinos run over to it, Gekko can trap them, and it will show everyone how strong he could be. Concerned about this, Owlette asks if she and Catboy can help out, but Gekko declines and asks them to stay behind, since this is all about his super strength. Although surprised at his statement, Catboy and Owlette comply and hide behind a couple of bushes, while Gekko walks over to Night Ninja and his Ninjalinos, who are now at the sports hall.
As the Ninjalinos do their training, while at the same time treating Night Ninja, Gekko calls on them. He challenges them to a flex-off, and runs away. In response, the Ninjalinos follow him, as Night Ninja intends them to catch him and show off their improved strength. Gekko goes into the forest, activates his Super Gekko Camouflage, and waits off while the Ninjalinos continue running. Once they reach the trap, Gekko reappears, grabs the rope of the trap, and uses his Super Gekko Muscles to pull it, closing the trap around them and lifting them off the ground. It works, until Night Ninja commands them to jump. They comply, and jump in unison, which lowers the trap by a little bit. Catboy and Owlette run over to help Gekko out, but he refuses, saying that he is super strong to handle it. Unfortunately, because of the Ninjalinos' improved strength, Gekko cannot hold them down. With a few more jumps, the trap goes down, and the Ninjalinos are free, while Gekko is thrown into the tree branch that the trap is hanging on. As he jumps down, Catboy and Owlette walk over to Night Ninja and the Ninjalinos, declaring that they can help take care of them. Unfortunately, Gekko still refuses, and gets ready to take on them himself. Amused by his determination, Night Ninja orders the Ninjalinos to get him. Four of them jump over to Gekko, grab him, and carry him. Catboy and Owlette try to rescue him, but a couple more Ninjalinos push them back. Soon, they watch the Ninjalinos playing with Gekko, treating him as a piece of sports equipment. Night Ninja watches as well, and is very proud. Now that the Ninjalinos are stronger than ever, they will soon be able to defeat anyone that comes in their way, except for himself. With that, he and the Ninjalinos take off, and Catboy and Owlette run over to Gekko as the Ninjalinos throw him up in the air. After the team catch him, Gekko is disappointed at what he did. All he wanted to do was show everyone that he is super strong, but because of that, he did not let his friends help out. Now that the Ninjalinos are now Super Ninjalinos with their strength, the sports equipment will never be retrieved, and no one will be able to stop them. Suddenly, he realizes something as Catboy points this fact out: the Super Ninjalinos are strong, and especially when they are together. That being the case, the PJ Masks can be strong as well, as long as they are together. With that, he comes up with a plan.
A few moments later, after looking around, the PJ Masks walk over to each other and show what they found: an old and broken jump rope, a broken bike, and a burst beach ball. With those things, they run over to Night Ninja and the Super Ninjalinos. In the forest, the Ninjalinos are still doing their training, while they still continue to treat Night Ninja. As they do that, though, Gekko yells out. With the PJ Masks, he reveals some more sports gear that they can have. Night Ninja refuses to have it at first, but sees that the Ninjalinos are eager to use it. He then accepts the equipment, and the Ninjalinos go after it. In response, the PJ Masks split up, making the big group of Super Ninjalinos split up into smaller groups. Once the action is done, this means that the Ninjalinos have grown weaker. With that, Gekko grabs the small group of Ninjalinos that is coming after him and throws them in the trap that is now hanging on a tree. Catboy comes over with the next small group of Ninjalinos chasing him, and Gekko throws them in as well. Owlette uses her Owl Wing Wind to blow the last small group of Ninjalinos towards him, and he throws them in. Now that all of the Ninjalinos are in there, and with the trap being held by the tree this time, they are not going anywhere at all. The PJ Masks celebrate at this, but Night Ninja stops them, saying that he is the one who the Ninjalinos should be practicing with. Owlette agrees, and throws all of them out of the trap and towards him. Once everyone piles up on top of him, this gives the PJ Masks a chance to grab the sports equipment. Fortunately for them, the Ninjalinos run off with Night Ninja, who are ready to practice with him, although Night Ninja himself does not want to practice with them all at once. Now that the sports equipment is retrieved, the Ninjalinos will lose their strength as time passes. With that, the PJ Masks cheer out their signature victory phrase.
The next day, Sports Day is back on at the park. With the sports equipment now returned, everyone will now be able to exercise and get fit and strong. Greg attempts to lift his bike again, but Connor and Amaya help him out. Even though Greg may not get that strong, he still has his friends to help him out. With that, the three kids laugh, and the episode ends.
Teamwork often helps in many situations.