Summary The summer idyll shortly before the election of the Dahlia Queen on the island of Mainau is abruptly interrupted. Nele interrupts the technical discussion that her mother Mechthild is having with the island's owner Count Bernadotte. Bernadotte's head gardener Sven Gallus is pulled dead from the water not far from the island. It soon becomes clear that Gallus has been poisoned. The deadly and difficult to detect poison is extracted from the fruit of the castor oil plant, of which there is a specimen on the island of Mainau. The officials learn this from the introverted trainee Denise Munk, who soon comes under suspicion: Gallus apparently had problems with her, especially since the woman with a criminal record only got the job as part of her probation. Did Gallus want to fire Denise and that's why she poisoned him? Gallus' partner, the cook Cornelia Hegemann, is convinced of this, because losing her apprenticeship would have meant that Denise would have had to serve her prison sentence. Hegemann's son Philipp is clearly in love with Denise, who flees before being arrested by Julia Demmler. The circle of suspects is expanded when the police find out that Gallus grew a very special type of dahlia. His inconspicuous "Hilde" had a very tasty tuber and was worth half a million euros to an investor... Does Gallus' closest colleague Martin Proschalla know more than he admits? When Mechthild is finally knocked down in her private greenhouse and "Hilde" is stolen, Nele feels the ground pulled out from under her feet. She had previously argued loudly with Paul about the research. And now Denise is on the run again.

• Crime