When 42-year-old Sina Priemke is beaten to death in a forest, the trail quickly leads to the university where she taught as a lecturer in computer science. Shortly before her death, Sina listened to secretly recorded, obscene audio recordings between her superior, Professor Brenneisen, and a certain Melanie. This is why the professor is immediately targeted by investigators. As it turns out, all the students and Professor Brenneisen received these audio recordings at the same time. From whom? And who is the unknown Melanie? Neither Brenneisen, nor any of the students, nor Sina's brother André know her.