During recess at a Tampa, Florida, elementary school, eight-year-old Devon Butler wields a water pistol while pretending to be a policeman. In the bathroom, he runs into two older bullies who dunk his head in the toilet and throw him back outside. Fed up with Devon’s antics, Principal Fleming telephones his grandmother. On his way home, Devon and his friend, Raymond Sanchez, witness a real police chase as detective Nick McKenna speeds after a drug dealer in his Chevrolet Super Sport. That evening, Devon’s grandmother works another night shift at the hospital, leaving him alone to watch his favorite television series, Miami Vice. Using binoculars, Devon sees a suspicious black vehicle drive past his apartment and follows on his bicycle. Inside an abandoned warehouse, he watches as organized crime leader Vinnie Fountain murders the drug dealer Nick McKenna caught earlier that day. When McKenna later arrives at the scene, he is frustrated to learn that Devon is the only witness. At the police station, Devon is eager take part in a real investigation, but only agrees to reveal pertinent information if he is allowed to shadow McKenna. With no other leads in the case, Captain Rubio decides to let him ride along with McKenna for eight hours the next day. Insisting he be allowed to carry a badge and handcuffs, Devon bolts out of McKenna’s car to chase a mugger across town. However, once McKenna catches up, they realize the supposed thief was only a man attempting to reach his wife, who forgot her purse. To make up for the mistake, Devon reveals the name of Fountain’s associate, “Bobo,” and the duo track down two of three potential suspects. After finding the second “Bobo” in the midst of a domestic dispute, McKenna is impressed by Devon’s tact, but promptly returns him home at the end of the shift. As the detective drives away, Devon again notices the black car in his neighborhood and realizes Vinnie Fountain somehow knows he is helping the police. Devon finds Fountain waiting in his living room, posing as the new school counselor to ask why he was not in school that day. Devon pretends not to recognize the criminal, but informs his grandmother they are in danger. To keep him safe until the case is solved, Captain Rubio puts Devon under McKenna’s constant protection. At his apartment that night, the detective reluctantly reads Devon a bedtime story and tucks him under the covers, but is later startled when the boy awakens for a glass of milk. In the morning, Devon is heartbroken to discover that McKenna has dumped him off on the more paternal Officer McPhail. During their patrol shift, McPhail explains that McKenna developed a gruff demeanor after his partner’s death in a violent drug arrest. As Devon issues a speeding ticket to Principal Fleming, two of Fountain’s henchmen attempt to run him over, but McKenna appears and pushes Devon to safety. McPhail pursues the criminals while Devon and McKenna continue their search for Bobo at a grungy biker bar. A fight breaks out, allowing Bobo to escape on his motorcycle. Back at his apartment, McKenna becomes upset when Devon sneaks away to buy donuts. He screams at the boy, offering to pay for him and his grandmother to move away, but Devon refuses, having likened the detective to a father figure. Running away, Devon sneaks back to school to retrieve items from his locker. When accosted by the two bullies from the bathroom, he retaliates by handcuffing them to the fence. Fountain’s henchmen arrive, but the other schoolchildren execute various pranks to keep them from finding Devon. Leaving the playground in shame, the gangsters discover the boy hiding in the back seat of their car. Captive inside Fountain’s Tampa Port Authority office, Devon finds a telephone and calls Captain Rubio to warn that Fountain is a drug baron. Meanwhile, McKenna spots Bobo on his way to Fountain’s warehouse, and sneaks inside. Grabbing Devon, McKenna escapes on Bobo’s motorcycle then hijacks a speedboat. With McKenna nursing a gunshot wound in the shoulder, Devon steers the boat through the harbor. At a dead end, McKenna encourages the boy to speed up two inclined pipes onto the docks. When Fountain and his men attempt to imitate the maneuver, they crash into a shipping container, and Devon pulls a lever that douses them in fish entrails. As backup arrives, Devon decides to “put police business on hold” and enjoy “being a kid.” McKenna agrees, but the two continue their friendship by spending a leisurely day with Devon’s grandmother.