In his room at a nursing home, Allan Karlsson sits quietly, waiting for a celebration he doesn’t want to start. More specifically, for his hundredth birthday party. The mayor will be there. The press will be there. But as it turns out, Allan will not be there. Through his bedroom window, Allan escapes into the flowerbed and sets off. Thus begins his picaresque and unlikely journey, which involves criminals, several murders, a suitcase full of money, and incompetent police officers. As Allan's escapades unfold, his past life is revealed—a life in which he notably played a key role behind the scenes of some of the most significant events of the twentieth century.