Jon Aldrich is a successful stockbroker in Chicago, Illinois, living with a beautiful wife, Audrey, and two children, while Jon’s parents, Harry and Mildred, and his divorced sister, Arlene, live in Florida. Jon has not seen them in several years and has neglected to tell his parents that he sold his father’s shoe store to become a stockbroker. When Jon receives an emergency telephone call that his mother is hospitalized, he immediately flies to Florida. Jon is unaware that his co-worker, Ed, is an undercover agent for the Federal Bureau of Investigation (FBI), and conducting a raid at the office that morning. At the private hospital, the administrator asks for Jon’s credit card to cover Mildred’s expenses, but the card is declined and he writes a check. Mildred is sedated for surgery, but admits she is worried about her husband, Harry. While Mildred is in surgery, Jon goes to the mobile home park to see his father. Harry is slow to recognize his son, but seems happy. Jon wants to speak with his sister Arlene and asks Harry to drive him. Excited, Harry backs his prized Cadillac out of the driveway and speeds in reverse until he crashes in the water. As the car is towed out, a doctor places a patch over Jon’s wounded eye. Jon leaves his father at the mobile home and visits his sister. Arlene has little concern for her parents, declaring she is broke and attempting to move in with her new boyfriend before he discovers she has two rambunctious sons. When Jon returns to the trailer park, he discovers that his father burned down his mobile home while making lunch. The doctor reveals that Harry is physically fine, but suffers from senile dementia. As they return to the smoldering home, Jon is surprised to see his co-worker, Ed, and FBI agents searching through the wreckage, and examining his charred briefcase. Jon is stunned to learn that his “friend” is an undercover agent who believes Jon came to Florida to destroy evidence and leave the country. Jon denies the accusations. However, Ed refuses to listen and Harry continually declares that Ed is tied to the Mafia. At the hospital, Jon’s check has bounced because the FBI has frozen his accounts. Mildred is transferred to a county facility for her kidney stone procedure, and is unsurprised to learn that Harry burned their home. She reveals that Harry’s disease began eight years ago and has recently worsened. He can clearly remember his exploits as an aviator during World War II, but cannot remember the recent past. Jon takes his parents to Arlene’s place, but she pretends not to be home. Driving the Cadillac, Jon takes his parents to Chicago, where they meet Audrey and his children. Audrey is surprised to learn that she is Jon’s second wife, as he never mentioned his first marriage. She is equally surprised to discover Mildred and Harry will be living with them. In the morning, Jon awakens and discovers that his father has left the apartment with the children. Jon sees Harry crossing the busy street with the toddlers, and he runs outside to save them. Jon takes his father to work, and they are surrounded by reporters as they arrive. Inside, several co-workers are arrested, as Ed and his agents close the office. Ed apologizes for believing Jon was involved. However, he insists Jon must have been aware of the illegal actions, and admits that the government is keeping Jon’s accounts frozen, and his credentials to trade stocks are suspended. While Ed and Jon argue, Harry leaves the office. Jon sees his father talking to reporters, and races outside as Harry gets on a bus. Harry travels to his former shoe store, and believing it is still his, goes to the basement storeroom and retrieves a McDonnell Douglas bond that he hid years earlier. Pocketing the bond, he heads upstairs. Jon arrives as his father angrily notes the shoes are “junk” and a fight breaks out with the new owners. Jon gets his father outside and reveals he sold the store eight years earlier because it was not worth much anymore. Harry is surprised and declares it is worth $500,000. He mentions McDonnell, but Jon mistakenly assumes his father wants to eat at a McDonald’s restaurant. Later, Harry has a rare moment of clarity and tells Jon that he knows he is losing his mind. He does not want to live like that and asks Jon to end his life. As Jon refuses, the moment of clarity passes and Harry is “happy” again. That evening, Harry finds a gun in Jon’s closet and pockets it. As the family watches television news, they see Harry’s interview outside Jon’s office. When questioned about the FBI’s investigation, Harry continually declared that the Mafia was responsible, and revealed his name and address. Two Mafia men arrive at the Aldrich apartment and attack Jon, breaking his hand. Harry pulls out the gun, randomly shoots, and the two lackeys run away. Mildred takes Jon to the hospital where his broken hand is treated. Upon their return, the building manager hands Jon a thirty-day eviction notice, and he discovers that Audrey is taking the children to her sister’s home. She is fearful for their safety and leaves while Jon works out the situation with his parents. As Audrey leaves, Jon’s sister Arlene arrives with her boys and declares that they are moving in. Jon refuses and while they argue, Harry sneaks off. Jon sees his father outside. He rushes onto the balcony, falls over the edge, lands on a flagpole, and falls to the ground. He awakens in the hospital to discover surgeons have removed one testicle and a toe from his broken leg. As Jon recuperates, Fred, the freeloading doorman, begins dating Arlene and moves into Jon’s apartment. However, when Jon’s car and furniture are repossessed, Fred dumps Arlene and moves out. Moments later, Ed arrives and announces he made a deal for Jon to get his possessions back if he will wear a wire and entrap other stockbrokers. Arlene and Ed are instantly attracted to each other, and go on a date. At his wit’s end, Jon smashes the wiretap. Mildred hates to see her son so upset, and reveals that she and Harry thought of jumping off the balcony, but realized that Jon and Arlene would not get any insurance money if they committed suicide. She asks Jon to stage an accident so he and Arlene can make a double indemnity insurance claim. Arlene is excited by the idea, but Jon is upset. Mildred insists that she and Harry do not want to be a burden and will be happy if they can die together. Reluctantly, Jon agrees. However, his attempts to kill the couple all fail. They survive a car crash, befriend a dangerous motorcycle gang, and accidentally escape an explosion. Jon realizes he does not want to kill his parents, and declares he will not try again. However, Arlene insists on taking over. Audrey unexpectedly returns home, apologizes for leaving, and declares her love for Jon. While Jon talks with Audrey, Arlene sneaks off with Mildred and Harry. Jon and his wife race to stop Arlene’s plan, and arrive at an airport run by one of Harry’s World War II friends. As Harry and Mildred taxi down the runway, Jon jumps on the plane and Mildred lets him inside. He declares his love for his parents and insists a family must take care of each other. Harry believes it is 1943 and he is flying in battle. Mildred and Jon play into Harry’s delusion and eventually he lands the plane safely. John and Audrey purchase a home in the country, with a yard large enough for Mildred and Harry to live in a mobile home. Ed arrives to pick up his fiancée, Arlene, and her boys, and Jon thanks him for reinstating his stockbroker credentials. Before leaving for his new job, Jon places an identification bracelet on his father’s wrist so he will not get lost. As they talk, Jon again assumes his father is referencing McDonald's, until he sees the McDonnell bond worth a fortune.