 At Photo studio P. van Straaten, two models, Jacky and Penny, are dressed in Lederhosen to film a muesli ad. A missing prop, William Tell s arrow, is found lodged in the chest of Mabel de Ruijter, the studio s owner. Inspector Jeanine Kaart and her assistant De Bruin round up the suspects. Mabel s widower Ralf is already busy flirting with Penny. Nephew Paul, the photographer, is planning to marry Jacky, while his assistant Suzanne also has a reason to despise Mabel.