Sophie is amazed when the quirky ornithologist Professor Franzen appears at the station and has Dietmar and Bärbel imitate bird calls - apparently a ritual with tradition, because Prof. Franzen comes by once a year together with a group of students to inspect the extraordinarily rare bluethroat in to watch his nesting refuge in Hengasch. Unfortunately, the fun of the ornithologists is short-lived, because one of the students is found dead in the woods. Initially, Prof. Franzen is targeted by Sophie because very compromising photos show him in a bird costume together with the dead woman.
