Dr. Jack Hammond has best chances to become medical superintendent in the clinic. So he's completely absorbed in his work and has no understanding for his teenage son Chris' problems with school. By accident one of them drinks a brain-exchanging serum, and it switches their identities. This leads of course to extraordinary complications in school and at work, but also to insight in the problems and feelings of each other.

By accident, the content of a computer encyclopedia is transferred into the brain of Dexter Riley, a less than average college boy. Because of his newly acquired knowledge he competes in a quiz show between various universities, where he sweeps all the points. A wiz kid from another university finds out about his cheated wisdom and does everything to discredit Dexter.