The Soccer Monster steals Uniqua's soccer ball, so Monster Detective Tyrone helps Uniqua get it back.
Pablo comes out of his house wearing a worn-out green soccer jersey with a number '2' on it. He introduces himself to the viewer as the "soccer monster" and tells the viewer how he loves to play soccer. He sings the song I'm a Soccer Monster. He then spots a pink soccer ball and kicks it once. He kicks it again and tells the viewer that he wishes that there were another soccer monster to play soccer with him, and says that he is heading to his Soccer Monster Castle. As he walks off, his old shoes leave tracks of mud on the grass.
Uniqua walks out of her house to play with her soccer ball, and realizes that it is missing. She introduces herself to the viewer and looks around for her ball. Tyrone comes out from behind her wearing a brown detective hat. He asks Uniqua what she is doing, and Uniqua answers by telling him that she can't find her soccer ball. Tyrone tells Uniqua that he is a trained professional detective, and shows her a badge to prove it. Tyrone asks Uniqua to tell him the whole story, and Uniqua does as she is asked. Tyrone writes down what she says on a small notebook. Tyrone tells her that the Soccer Monster must of stolen it.
The backyard transforms into a large brown forest. Tyrone starts to sing The Rules, as he explains what Uniqua must do to sneak into the Soccer Monster's castle and retrieve her soccer ball. He tells her Rule Number 1: Be Quiet, and warns her with Rule Number 2: Do not play with the Soccer Monster. In the song, Tyrone explains to her that if she does, she will become a monster too. Uniqua asks a lot of questions until they reach the castle. Tyrone opens the door quietly and they sneak inside. Tyrone tells her to remember the rules. Uniqua spots two posters of Pele and Mia Hamm, two of the world's greatest soccer players, and recognizes them immediately. She starts to sniffle.
Tyrone asks Uniqua why she is sniffling, and she answers the question by telling Tyrone that it is dusty inside the castle, and dust makes her sneeze. Tyrone, surprised, tells her not to sneeze and to remember Rule Number 1: Be quiet. The two start to search the rooms to find Uniqua's stolen pink soccer ball. Meanwhile, Pablo the soccer monster is playing a game of soccer by himself in the castle gym. He scores a goal. The camera turns back to Tyrone and Uniqua, searching a small room containing a bookshelf and a sofa. Uniqua spots four trophies on a counter. Tyrone tells Uniqua that they have no time for trophies and have to continue their search. Uniqua picks up a gold trophy with a statuette of Pablo on top as Tyrone exclaims "Uniqua! NO!". The trophy falls to the floor and breaks in half. Pablo hears the shattering noise from the gym and stops his game of soccer.
Pablo is alarmed that there may be more people inside the castle and runs from the gym to find the visitors, without knowing who is in the castle as well. "I didn't mean to break it, I just wanted to hold it!" Uniqua tells Tyrone. He calmly tells her Rule Number 3: Don't touch anything. Tyrone bends down to put the trophy back together, but stops as he hears Pablo yell "Soccer!". They run into the main hall of the castle. Pablo opens the door to the room Uniqua and Tyrone were searching in before and spots the broken trophy.
Pablo now knows that others entered his castle and walks towards the main hall. In the hall, Uniqua sees a poster of the soccer team Manchester United. They hear Pablo again and dash behind a case. Pablo approaches them. Uniqua starts to sniffle again, because of the dust around her. Fortunately, she is able to prevent sneezing. After Pablo leaves to look in a different section of the castle, Tyrone compliments Uniqua on keeping quiet. Uniqua forgets to still be quiet and yells "Thanks!" loudly.
Tyrone covers his lips with his fingers as a signal to keep quiet. Uniqua then tells Tyrone that the monster does not look scary. Tyrone reminds her that she will become a monster as well if she joins him in a game of soccer. To keep Uniqua from getting bored and deciding to play with the Soccer Monster, Tyrone tells Uniqua that their job is like hide-and-seek, because they hide from the monster while seeking Uniqua's soccer ball. Uniqua adds that the monster is seeking them.
Uniqua and Tyrone start to sing Hide and Seek. Uniqua opens a door and spots the Soccer Monster and points to him. The two run back out the door as the monster walks into the room Tyrone and Uniqua are hiding in. Uniqua and Tyrone hide behind a couch as the Soccer Monster looks around. The monster thinks that they are playing hide & seek and covers his eyes and counts to ten. The two run out the door when he says "three". Pablo opens his eyes and sadly tells himself that he doubts that he will ever play soccer with someone else.
Uniqua and Tyrone are hiding. Uniqua sneezes and Pablo hears her. He runs into the room they are hiding in. Pablo hands her a box of tissues and Uniqua thanks him. Tyrone pushes Uniqua and tells her to run. Uniqua does run away from Pablo. Pablo the Soccer Monster runs after them. Uniqua and Tyrone enter the gym and shut the door behind them. Uniqua is amazed at how much balls the monster has. They look for her pink soccer ball. Uniqua finds her ball, but Pablo opens the door and chases her. Uniqua and Tyrone run toward the right goal net, then turn around. The Soccer Monster bumps his head on the side. He continues to look for them, but Uniqua and Tyrone hide amidst the soccerballs in the wooden box. Pablo spots them and Tyrone runs out the door. Pablo notices and sadly asks himself why no one will play with him.
Uniqua looks at Pablo compassionately and tells him that she will play with him. Tyrone begs her not to, but Uniqua plays soccer with him. Uniqua turns into a soccer monster, now wearing a worn-out green jersey with a number '1' on it. "Soccer!" cries Uniqua happily. Uniqua and Pablo run to Tyrone, but Tyrone runs out the door screaming. Uniqua asks Pablo if they should chase him, but Pablo answers no. They play a game of soccer while singing a new verse of I'm a Soccer Monster. Tyrone looks back inside the gym and tells himself that he is "out of here". But he argues with himself and tells himself that he needs to get the job done as he sings Gotta Get the Job Done.
Tyrone walks back inside and yells to Pablo that he has snitched his last ball and he has to give the ball back to Uniqua. Pablo passes the ball back to Uniqua. They start to play soccer, but Tyrone interrupts by asking them if anyone has to be a monster to play soccer. They let him play and sing another verse of I'm a Soccer Monster. Tyrone turns into a soccer monster, now wearing a worn-out green jersey with a number '3' on it. Tyrone invites the other monsters over to his house for celery with hummus. They all accept as the gym transforms back into the backyard. They sing the end song and enter Tyrone's house. Pablo opens the previously closed door and shouts "SOCCER!".