Peter Beaupre, Alice Ribbons, Burton Jernigan, and Earl Unger are four internationally wanted spies working for a North Korean terrorist organization. After stealing a $10 million missile-cloaking microchip, the spies put it inside a remote control car to sneak it past security at the airport. However, a luggage mix-up causes an elderly woman named Mrs. Hess to inadvertently take the spies' bag containing the car before returning home to Chicago. The four spies arrive in Chicago and systematically search every house in Hess's suburban neighborhood to find the chip.
8-year-old Alex Pruitt is given the remote control car by Hess for shoveling her driveway, but she lectures him for scratching in public. He returns home and discovers that he has chickenpox and must stay out of school. The next day, Alex discovers the spies while spying on his neighbors. After two failed attempts at reporting them, Alex attaches a camera to the remote control car and uses it to spy on them, leading to the spies chasing it when they spot it. Wondering what they want with the toy car, Alex opens it and discovers the stolen chip. He informs the local Air Force Recruitment Center about the chip while asking if they can forward the information about the chip to the right authorities.
The spies finally realize that Alex has been watching them and decide to break into his house. Alex rigs the house with booby traps with help from his pet rat Doris and his brother's loud-mouthed parrot. Beaupre, Alice, Jernigan and Unger break in, spring the traps, and suffer various injuries. While the four pursue Alex around the house, he flees and rescues Hess, who has been duct taped to a chair in her garage by Alice. Beaupre ambushes Alex, but the latter uses a bubble gun resembling a Glock to scare him off and rescue Hess.
Meanwhile, FBI agents arrive at Alex's siblings' school after being tipped off. Alex's family brings the agents and the police to their house, where they arrest Alice, Jernigan, and Unger. However, Beaupre flees to the snow fort in the backyard. The parrot drives the remote control car into the snow fort and threatens to light fireworks, which are lined around the inside. Beaupre offers a cracker in exchange for silence, but the parrot demands two. Since Beaupre has only one, the parrot then lights the fireworks and flees. Beaupre is discovered and arrested.
Later, the Pruitts, Agent Stuckey and Hess celebrate with Jack returning home from a business trip, while Alex's house is being repaired. The spies are shown to have contracted Alex's chickenpox during their mugshots.
Alex D. Linz as Alex Pruitt, an 8-year-old boy.
Haviland Morris as Karen Pruitt, the mother of Alex.
Olek Krupa as Peter Beaupre, the leader of the international spies.
Rya Kihlstedt as Alice Ribbons, a member of the international spies.
Lenny Von Dohlen as Burton Jernigan, a member of the international spies.
David Thornton as Earl Unger, a member of the international spies.
Kevin Kilner as Jack Pruitt, the father of Alex.
Scarlett Johansson as Molly Pruitt, the older sister of Alex.
Seth Smith as Stan Pruitt, the older brother of Alex.
Marian Seldes as Mrs. Hess, an elderly lady who is the Pruitt family's neighbor.
Christopher Curry as FBI Agent Stuckey, an FBI agent whose been after Beaupre.
Baxter Harris as a Police Captain
Neil Flynn, Nick Jantz, Tony Mockus Jr., and James Chisem as Police Officers
Freeman Coffey as Recruiting Officer
Adrianne Duncan as Flight Attendant
Jennifer A. Daley as Police Photographer
Darren T. Knaus as voice of the Parrot, a talking parrot owned by Stan.