On his first day as a fourth-grader, Sune is welcomed by an unwanted surprise. A new boy is in his seat, and he's everything Sune wants to be. Not only that, but his name is also Sune - it's the worst possible start to the fourth grade. Sune must use all his cunning to stop Sophie from breaking up with him and choosing the other Sune. At the same, Håkan notices that his big brother is about to enter the boring adult world, their dad Rudolf has a midlife crisis and wants to quit his job to pursue a career in music and their mum Karin glares jealously at the new Sune's perfect mum and her even more perfect car. Welcome to the Anderssons.