The Dortmund doctor, Dr. Michael Beyer, is surprised when he receives a peculiar inheritance. A patient has left him all sorts of junk in her attic, along with a letter containing a seemingly dangerous mission. He is to confront this task with the deceased's granddaughter, Eva Maybaum. Together, the two embark on solving the mystery, which has its origins in the 1970s. However, the closer they get to the truth, the more dangerous their investigation becomes.