Once down the coast, always along the sea. For Martin, 49, a rocked-out musician, one-hit wonder from 20 years ago, the route is fixed. His goal: a music festival in Portugal, his big chance for a comeback. When his sister asks him shortly before departure to take care of her son Karl during her rehab stay, the answer is clear: No. Martin doesn't need a 12-year-old at all right now. He puts the boy up with grandma and drives off, in his old station wagon, always heading south. But as soon as he is really on the road, a stowaway in the back seat makes himself felt: Karl has no desire at all to go on holiday with grandma, he is determined to come to Portugal with him. The two unequal travel companions - Martin, the child's head, and Karl, who is actually much too grown up for his age - set off on a journey full of adventures. They will help refugees, commit shoplifting, perform as street musicians. And Karl will fall in love for the first time, in the light of a bright summer that changes everything.