Just before heading off for a much-anticipated vacation, self-centered psychiatrist Dr. Leo Marvin encounters a challenging new patient: Bob Wiley. Bob, a walking encyclopedia of insecurities and fears, ends up tagging along to Dr. Marvin's family retreat. Despite the doctor’s attempts to send him away, Bob quickly becomes a beloved figure among Marvin's family. As his unwitting patient settles in, Dr. Marvin's sanity begins to unravel, pushing him to the brink of his own mental collapse.