At a Tempe, Arizona, police station, H. I. McDunnough flirts with a female police officer named Ed as she takes his mug shots. Although H. I. is paroled from his prison sentence, he is arrested again for robbing a convenience store and, back at the police station, he learns that Ed’s fiancé has left her. After a third parole and subsequent robbery, H. I. slips a ring on Ed’s finger as she takes his fingerprints and reassures her that it was not stolen. When H. I. is released from prison, the couple marries. They move into a trailer in the desert and H. I. finds work at a sheet metal factory. Although he and Ed enjoy married life, Ed longs for a child and is devastated to learn she is “barren.” The couple tries to adopt, but they are rejected as suitable parents because of H. I.’s criminal record. While Ed falls into a depression and quits the police force, H. I. finds himself driving past convenience stores, longing for his past life. Back at the trailer, Ed and H. I. see a newscast about the birth of quintuplets to Florence Arizona and her husband, Nathan Arizona, the owner of a successful furniture store called Unpainted Arizona. The couple decides to kidnap one of the “Arizona Quints” to fulfill their dream of becoming a family. At the Arizona household, Nathan takes a business call and Florence reads Dr. Spock’s Baby and Child Care while H. I. breaks into the nursery. As he takes the boys from their crib, mayhem ensues. Concerned by the noise, Florence checks the babies and H. I. returns to the car empty-handed. When Ed insists he try again, H. I. procures Nathan Junior and Florence’s Dr. Spock book for “instructions.” Although Ed hesitates, the couple returns home to the trailer, which they have decorated to celebrate the arrival of their new son. As H. I. sets up a family photograph, Ed says she is anxious about their parental responsibilities and asks H. I. for his complete cooperation. Meanwhile, H. I.’s prison friends, brothers Gale Snoats and Evelle Snoats, emerge from the mud outside of the penitentiary after a successful escape. Stealing a car, the brothers drive to H. I.’s trailer. Although H. I. is happy to see his friends, Ed realizes the brothers are escaped convicts and insists they leave. When Gale Snoats suggests H. I. is submissive to his wife, H. I. permits them to stay and promises Ed it will only be for a few days. That night, H. I. has an apparition of a menacing motorcyclist that kills innocent creatures in his path named Leonard Smalls. Fearing that Smalls is a physical manifestation of his inner demon, H. I. worries that he unleashed the monster by kidnapping Nathan Junior. At the Arizona home, Nathan gives a press conference and assures the public that Unpainted Arizona is still open for business. Meanwhile, highway patrol officers discover the Snoats brothers’ tunnel and Smalls, a bounty hunter, follows their trail. Back at the McDunnough trailer, H. I. asks the brothers to leave for the afternoon because they are entertaining company and, later, H. I.’s work supervisor, Glen, and his wife, Dot, arrive with their throng of rambunctious children. Preparing lunch, Dot overwhelms the new parents with a frenzied description of a baby’s needs. Later, H. I. confesses his apprehension to Glen, but when Glen suggests they swap wives, H. I. breaks his nose. Without knowing the reason for her husband’s actions, Ed later berates H. I. for jeopardizing his job. Pulling into a convenience store, H. I. relieves his anxiety by attempting to steal diapers and cash, but Ed sees him from the parking lot and drives away in anger. As the police arrive, H. I. runs from the scene, dropping the diapers, and when Ed hears gunshots, she turns around to save her husband. Chased by the police, H. I. heads to a supermarket for more diapers, but uses them to repel an officer. Dodging bullets, H. I. races to the parking lot, where Ed screeches to halt. As she drives away with her husband, Ed tells him that his criminal tendencies are not appropriate for family life. However, H. I. insists she must accept him and leans out of the speeding vehicle to collect the stolen diapers he dropped. Back at the trailer, Ed orders Gale and Evelle to leave the following morning. When she retires, Gale suggests that the couple’s marital friction might be resolved by financial security and proposes that H. I. help them rob a bank. Showing H. I. a newspaper clipping, the brothers explain that all the local farmers will be cashing in their subsidy checks the following day. Although H. I. is hesitant to defy Ed, Gale convinces his friend that he is not being true to himself by living a straight life. Late that night, H. I. writes a farewell letter to Ed, claiming that he cannot be a responsible parent. Meanwhile, Smalls drives to the trailer, camps outside, and hears the cries of Nathan Junior. The next day, Smalls barges into Nathan Arizona’s office and describes himself as a man hunter. He claims that Nathan’s $25,000 reward is not commensurate with the market value of a baby and offers to return the child for $50,000. When Smalls threatens to sell the boy on the black market, Nathan suspects him of being the kidnapper and calls the police, but Smalls disappears. Meanwhile, Glen arrives at the McDunnough trailer to fire H. I. and announces his discovery that the baby was kidnapped. Instead of returning Nathan Junior for the reward, Glen has decided to keep the baby and gives H. I. one day to inform Ed. Meanwhile, the Snoats overhear Glen’s threats and decide to take the baby, themselves. After H. I. fights Gale, the brothers tie him up and take Nathan Junior, along with the Dr. Spock book. On the road, Evelle robs a grocery store for diapers, but the brothers forget to put the baby back in the car and drive away with his car seat still on the roof. As the brothers speed back to the store, they come within inches of colliding with Nathan Junior, whose car seat is resting in middle of the highway. Ed drives after the brothers in her police uniform and tells H. I. that they must return the baby. Even though she still loves H. I., she wants to end their relationship. Back at the trailer, Smalls discovers the Snoats brothers’ newspaper clipping and heads to the bank where Gale and Evelle are holding up a group of farmers. A teller slips a combustible dye pack into their loot bag while filling it with cash. As the brothers drive away, they realize that Nathan Junior was again left behind and the canister explodes. With blue paint obscuring the windshield, the brothers nearly collide with Ed and H. I., who hold them at gunpoint and demand to know the baby’s whereabouts. H. I. and Ed speed toward the bank, but Smalls approaches Nathan Junior from the opposite direction and retrieves him first. Shooting out H. I. and Ed’s car windows, Smalls throws a grenade inside the vehicle, which explodes shortly after H. I. and Ed run to safety. When Ed confronts Smalls, H. I. shoots a knife from his hand and Ed retrieves the baby. Smalls chases Ed through the bank on his motorcycle and H. I. knocks him off the bike as he returns outside. While the men fight, H. I. observes that Smalls has an identical tattoo to his own. Smalls prepares to finish off his adversary, but when he notices that H. I. pulled the pin from one of his grenades, Smalls explodes. Sometime later, H. I. and Ed return Nathan Junior and Florence’s Dr. Spock book to the Arizona home, but Nathan discovers them in the nursery. H. I. explains that they saved the baby from Smalls, but declines to elaborate. When Nathan offers the couple furniture in lieu of reward money, Ed refuses and Nathan realizes they are the kidnappers. Ed tearfully tells Nathan they were unable to conceive and H. I. says their marriage is over, but Nathan suggests the couple “sleep on it” before making a final decision. That night, H. I. dreams of the future where the Snoats brothers voluntarily return to prison, Nathan Junior receives a football as Christmas gift from an anonymous couple, and Glen unsuccessfully attempts to implicate H. I. and Ed in the Arizona kidnapping. Further into the future, H. I. envisions Nathan Junior as a star football player. At the end of his dream, H. I. sees himself and Ed as an elderly couple with children and grandchildren.