Chance the gardener has lived his entire life in the house of the Old Man, but when the Old Man dies, Chance is turned out by the lawyer for the estate. Chance is illiterate and incredibly simple-minded, and aside from gardening, his only life experience is watching TV, learning about the outside world from what he sees on the tube. Walking the streets aimlessly, he is struck by a limousine belonging to Elizabeth Rand, the wife of a wealthy industrialist. When he is asked his name, Chance responds "Chance the gardener," but the Rands mistake it for "Chauncey Gardiner," and a new man is born.
The Rands, though wealthy and highly intelligent, mistake Chauncey's simple explanations about life in the garden as deep-seeded metaphorical wisdom concerning business, society and politics. When the President of the United States visits Rand's home, he is equally impressed with Chauncey and mentions him in a speech that night. Chauncey becomes an overnight sensation, quoted in news reports and appearing on TV. Elizabeth falls in love with Chauncey, who has no experience with love nor emotional attachment with anything but watching TV. Chauncey's celebrity status rises to new heights when he is considered as a top political candidate, and when his background is checked carefully by American and Russian sources, they can find no record of Chauncey (or Chance) having ever existed. This only makes Chauncey a more viable candidate, since there is nothing negative to be found in his past.