Sune's class is going on a secret school trip. Sune and Sophie are really looking forward to spending time together when Sune suddenly realizes that Grandpa Helmer's wedding is the same weekend. Panic. Class trip with Sophie or his best friend Grandpa? Sune can't make his mind up so decides to do both. Or something in between. At the same time Rudolf is suspicious about the bride. Is Grandpa's new wife just after his money? And Karin runs into her former love, who is everything that Rudolf is not. Welcome back the Andersson family.