Alvarito, an apparently normal boy with a perfectly sane brain, suffers nonetheless a mysterious chronic stupidity that eludes the limits of modern medicine. Florentina, his dedicated mother, after years of infructuous search for the causes of her son’s disorder, decides to pawn her last properties and resort to the consultation clinic of Dr. Natalio, a barber-surgeon of infamous reputation to whom are attributed as many miraculous healings as obscure negligences. Dr. Natalio, widely schooled in quackery and medieval surgery, doesn’t have a doubt about his diagnosis: Alvarito suffers the disease of the “stone of madness”, a pebble that presses the brain, impeding correct reasoning to the patient. According to his theory, an uncomplicated operation, as old as the world itself, will be enough to remove the stone and change Alvarito over a perfectly lucid young man…