Sitting quietly in his room in an old people's home, Allan Karlsson is waiting for a party he doesn't want to begin: his 100th birthday party. Escaping through his bedroom window, into the flowerbed, Allan makes his getaway. And so begins his picaresque and unlikely journey involving criminals, several deaths, a suitcase full of cash, and incompetent but very human police. As his escapades unfold, Allan's earlier life is revealed, and we discover that he played a key role behind the scenes in some of the momentous events of the 20th century.