Karin Hoehne is a retired teacher living in Berlin - Haselhorst. On her way to meet her best friend Rosa Brathuhn she involuntarily witnesses a horrible murder on a passing train. A young woman gets chopped up by an ax murderer. Sadly the police, in particular exchange commissioner Rock Milchester, thinks that she is a slightly senile old lady, especially because no corpse was found. So what else can she do but to try to solve the case on her own.