People discover that they can gain another person's knowledge and skills by eating their brains. This forces educated people to hire bodyguards, wear disguises, and go into hiding, because everyone is after them to eat their brains. A society develops in which everyone pretends to be stupid and ignorant; every interaction is rife with danger (and humor) because revealing your education puts you at risk of being eaten. Knowledge becomes concentrated in the minds of cannibals. But of course, those brain-eaters will be targeted for THEIR erudition.
The hero could be a child whose parents, without his knowledge, nursed him on the brains of the brilliant.
I hereby bequeath this idea to the public domain.