PERCY, BUFFALO BILL & IUlf thought that this summer was going to be like all the others. He would go, as always, to his grandparents home on the Schaeren islands, quarrel with his brother, have fun with his friends and listen to his grandfathers farting at night. But this time things are a bit different, because Ulf has recently acquired a blood brother, named Percy. Do you know what it means? Percy asks. But Ulf doesnt have a clue until his blood brother explains:
It means you have to spend the entire summer together. And so, Percy, who doesnt have anyone to go away with, accompanies Ulf to his grandparents place. Ulf warns his blood brother about his cantankerous grandfather, who hates dogs, children and adults. In fact, he hates everyone and is always at loggerheads with someone. The only person he cares about is grandmother. But she doesnt want to know, and this makes him hate the rest of the world even more. In spite of this, Percy manages to befriend the gnarled old man, who enjoys telling him about the time when, as a child, he paid a visit to the circus where he saw the legendary Buffalo Bill. And then theres Pia, in whom Ulf has fallen in love, and who is not allowed to dance with Percy. Suddenly, grandfather is struck by lightning and his behaviour starts to change in a most mysterious way. All at once, the summer turns out to be an unforgettable experience for all concerned.