Rowdy Jonas, 11, longs to spend the summer exploring the Slovakian countryside with his cool Grandpa Bernard, but his exasperated mother plans for him to go to the seaside instead. Jonas sneaks away from home and takes the train by himself to his grandpa’s. Upon arrival he finds his grandpa grumpy and moping. Luckily, his brave and tomboyish neighbor Alex befriends Jonas and together they create a scheme to raise money for a raft of their own. Their illegal racket creates an uproar in the village, lands Grandpa in jail for a crime he didn’t commit and causes Alex and Jonas’s friendship to fray. Will Jonas find a way to repair the mess?