Professional psychologist Dr. Leo Marvin (Dreyfuss) is getting ready to go on a family vacation at his summer home, and getting ready for a live interview with Good Moring America. A few hours before he leaves, a seemingly traumatized colleague leaves a new patient on his doorstep. The patient is Bob Wiley (Murray), a lovable, walking encyclopedia of fears, and problems. shortly after Bob meets Leo, Bob follows him to his vacation spot. In the process of driving Leo to insanity, Bob charms Leo's wife and kids, steals the spotlight on Leo's interview, blows up Leo's house, and marries Leo's sister, Lily.