Maren Hilbert starts her new job as a music and German teacher at the private school "Sophienbund". She soon finds a good rapport with her class thanks to her unconventional manner, but she also notices that the relationship between her 16- to 17-year-old students is not the best. One morning, she receives a call from the school secretary's office, which is still unmanned, in which an anonymous threat of a killing spree is made.