Peter Beaupre is the leader of a group of thieves who have stolen a valuable Air Force computer chip. When a bag mixup at the O'Hare Airport in Chicago causes Mrs. Hess, a grouchy old lady, to unknowingly take home the chip hidden inside of a toy remote control car, Beaupre and his followers Alice Ribbons, Earl Unger, and Burton Jernigan begin searching Mrs. Hess's neighborhood and breaking into houses searching for the chip. 8-year-old Alex Pruitt reports seeing Beaupre and his followers, but Alex's sister Molly, his brother Stan, and his parents Jack and Karen refuse to believe him. Beaupre and his followers figure out that the chip is in the Pruitt home, because Mrs. Hess has given the remote control car to Alex. Alex is left home alone with the chicken pox when Karen goes to work, Jack goes out of town on a business trip, and Molly and Stan go to school. When Beaupre and his followers break into the Pruitt house, Alex is ready with some of the most painful booby traps Beaupre and his gang will ever face.