In the 9th book of the bestselling series, the Kaminski kids encounter a surprise during their summer vacation in Amsterdam. The boy Sven still has a score to settle with them because they contributed to his arrest for ecstasy trafficking. However, he has since been released from custody due to lack of evidence and now wants to collect his debts from the kids. Together with their friends Mark and Antje, the Kaminski kids come up with a plan: they want to lure Sven into a trap, aiming to ensure that this time he is caught with solid evidence, so he no longer poses a threat to them. But first, they need to find him. The search takes Simon, Debora, and Raffi, along with their collie Zwockel and their friends, through the romantic streets, canals, and arched bridges of the Dutch capital, until they finally track Sven down in the Chinese quarter.