Christian “Mac” Barrett is a sixth-grader who knows how to solve problems. He and his best friend, Vince, run a fixing business out of a little-used boys’ bathroom in their middle school.
One afternoon, a student named Robert asks Mac to get him and a girl into an R rated movie. Mac agrees in exchange for $5 and a favor to be called in down the road. Robert agrees.
The next customer is Fred, a third-grader. He’s been working as a bookie for a guy named Staples. Fred wants out of the business, but Staples is refusing to let him go. Staples is a legend that most kids think is a myth. Fred says that Staples has bookies in all the local schools and has been taking bets on high school and middle school sporting events and then fixing the games in his favor.
Mac is hesitant to get involved, but decides to help protect Fred. Mac gets Brady, another third-grader, to watch Fred during class and decides to keep Fred in the office with him and Vince during recess.
The next day, Barnaby Willis, one of Staples' goons, ambushes Mac as he’s going into his office. Barnaby tells Mac that Staples knows he’s helping Fred. Vince arrives before Barnaby can become violent, and Barnaby runs off. Not only is Staples bad for business, he’s dangerous. Mac is determined to take down Staples. He asks Fred for more information about Staples and his business. Fred doesn’t remember much, but says that Jacky Boy is another bookie at the school.
Hoping for more information, Mac and Vince go to see Ears on the playground. Ears is their top informant. When Ears sees them, he takes off running. Mac and Vince catch him and discover that Ears is deep in debt with Staples. To pay his debt, he turned on Mac and has been passing information to Staples.
Mac, Vince and their strongman, Joe, walk Fred home after school. Barnaby and four of Staples’ high school guys jump them, but they manage to escape. Mac decides it’s time to take Barnaby out of the equation. He hires nine of the school’s bullies and tasks them with getting rid of Barnaby. At recess, the bullies carry out their mission. They are so thorough that Barnaby transfers schools.
Mac has a bully named Kittens bring Jacky Boy in for questioning. Mac pretends he wants to partner up and asks for a meeting with Staples’ top guy in the middle school. Jacky Boy reveals the head guy’s name is Justin. Mac places a bet with Jacky Boy and says he wants to do the same with all the bookies in the school as a sign of good will. Jacky Boy reveals the names and locations of all the bookies.
Mac sends the bullies after the bookies in his school. While he watches them do their work on the playground, a seventh-grader attacks him. Kittens stops the attack, and the kid reveals that Justin knew Mac would be on the playground during recess instead of in his office. After school, Mac finds his hired bullies beaten and tied up. Staples sent guys after them, and most of the bullies don’t want to work for Mac anymore. Mac realizes he has a mole feeding information to Staples.
Staples goes to Mac’s house pretending to be a friend so Mac’s mom will let him in. He tells Mac that he’s going to ruin his business unless Mac comes to work for him. Mac refuses, and Staples leaves.
That night, Mac is going over his books and discoveries a balancing error. When he asks Vince about it, Vince claims it must be a simple mistake. Mac compares Vince’s book with his own and realizes that Vince has been fixing the numbers so he can steal money. Mac confronts Vince. Vince reveals that his mom lost her job, and he was taking money to help make ends meet. Mac forgives Vince, but he doesn’t forget the betrayal.
At recess, Mac puts his plan to take down Justin into action. He plans to ambush him with the bullies. The mole tells Justin about the plan, and he arrives with backup and locks the bullies into the shed where they’re hiding. Justin and his gang beat up Mac.
Mac hires Tyrell to follow Vince, Fred and the others involved with his business to discover who is the mole. Tyrell enjoys spying on people and is very good at it. Tyrell comes back with a video of Vince meeting with Staples and taking money. Mac sneaks out of school and goes home to check on the money from the business and finds that it’s all missing. He believes Vince stole it. Mac confronts Vince, who denies the accusation.
At school, Mac tells his friends that without money he can’t run his business. Mac sets up a meeting with Staples to discuss working together. Before the meeting, Mac realizes he has one favor to call in that could save him. Robert, a kid he helped before the Staples' issue, is the son of a police officer. He asks Robert to use his father’s resources to find anything he can on Staples.
Robert calls that night. Staples’ real name is Barry, and he has a long police record. If Barry gets caught doing one more illegal thing, he’s going to prison. Robert also get’s Barry’s home address. With Tyrell’s help, Mac goes to Barry’s home and finds his office.
Mac finds a gaming device with messages from Fred on it. Fred was the mole sent to infiltrate Mac’s business. He has been spying on Mac the whole time. Realizing that Vince is innocent, Mac apologizes to his friend and the two reconcile.
When Staples shows up for the meeting, Mac reveals all he knows about Staples’ true identity and Fred’s betrayal. During this time, Mac's people go to Staples’ office. They find Mac’s stolen money and all of Staples’ books.
Mac tells Staples to stop working in his school and leave his friends alone or he’ll take all the information he has to the police. Staples doesn’t believe Mac. He grabs Mac and forces him to a vacant lot outside of town where his high school goons are waiting.
Before Mac is beaten up, Vince arrives with some of the bullies hired by Mac. Kittens takes a metal rake and threatens to destroy one of the boy’s cars. All of the goons decide the confrontation isn’t worth it and abandon Staples.
Staples reveals that everything he’s done is to help get his sister out of foster care. Mac is sympathetic and offers to help, but Staples is too proud to accept. Mac keeps Staples’ books so he has leverage against Staples in case he starts causing trouble again.
With Staples out of the way, Mac and Vince’s business is back up and running. Life goes back to normal for the time being.