Tragedy strikes a small Kansas town when children begin disappearing. A young boy, Jason, constructs a theory explaining why children from certain neighborhoods go missing, which he calls the Topeka Triangle. Jason uses the Topeka Triangle to explain things that seem irrational to him, like his emotional outbursts, the missing children, and his mom’s marriage to his abusive step-dad.

Jason is unpopular at school. His peers deem him a know-it-all. They bully him until he cries. One of his bullies, Brendan, attempts to steal Jason’s walking stick on the way to school one morning. In a fit of anger, Jason attacks Brendan. Jason attributes his animalistic display of violence to the Topeka Triangle. After Brendan apologizes to Jason, they become friends and begin to play video games together after school. They talk about the children who have gone missing, one of whom is their shared crush Kim Davidson. Unlike the other missing children, Kim is from an impoverished background. Jason relays his Topeka Triangle theory. Brendan proposes that they solve the mystery together by conducting an experiment. 

When Jason comes home that night, he feels the power of the Topeka Triangle coursing through his being, causing him to threaten his step-dad, who took out his anger on Jason’s younger brother. The power shows up another time when Jason is out late at night to help some older kids steal cigarettes and an adult magazine, though this time it doesn’t cause him to do anything. Instead, the police show up on the side of the road and call his dad to take him home. The next morning, Brendan and Jason walk to school together. The fog is thick outside, burying their surroundings in a heavy layer. When Jason can’t see the school, he and Brendan wonder if the Topeka Triangle has taken it. Jason runs toward it, feeling for the first time that he has something to lose.