Sune and Sophie eagerly plan to celebrate Scandinavian Midsummer together with their families, but disaster strikes the day before departure when Sophie breaks up with Sune. Desperate to win her back, Sune turns to his little brother Hakan—an 8-year-old addicted to 1980s romantic comedies—for advice, sparking a chain of hilariously misguided disasters. Meanwhile, Sune's mother Karin inherits a cottage in the quaint village of Myshult, renowned for its epic Midsummer festivities, drawing the entire Andersson family and Sophie's clan for vacation. Yet Sune's romantic schemes only amplify the chaos, as he clings to hopes that the party will reunite them forever.

Compounding the mayhem, big sister Anna fears parents Karin and Rudolf are heading for divorce. To intervene, she acts out wildly, prompting the couple to genuinely question their bond. Tensions peak when Midsummer celebrations prove strictly forbidden in modern Myshult—but nothing deters the unstoppable Anderssons. Falling maypoles, unexpected twists, and non-stop antics ensue, turning expectations upside down. In this hilariously entertaining family adventure, young heroes brim with vitality and ingenuity amid a fantastic plot bursting with heart, humor, and action.

Following the box-office hits Sune vs. Sune and Sune – Best Man, SUNE – MISSION: MIDSUMMER—based on the internationally successful “Sune” book series—promises more crowd-pleasing chaos where mishaps lead to the best outcomes.