The family's long awaited holiday at The Wadden Sea is threatened, when Dad is accused of being a burglar. The family tries to prove his innocence - but Dad's unlucky actions make him look more and more suspicious. In the end, Lille Per has to take action with his own hands. He decides to commit a felony in order to the find the real thieves. This almost goes horribly wrong, and soon the entire island is convinced that Dad is guilty. In the end, when all hope of proving Dad's innocence is lost, Lille Per finds a crucial clue in the hunt of the real thieves. Therefore, a race against time begins; to make sure that the thieves does not escape the island.