Jan Casstorff is a police officer who broke off his psychology studies. He could be much higher up the career ladder if he had not made his duties as a single father his top priority. His colleagues appreciate his talent for precise analytical thinking and his value as a good friend but they have trouble overlooking his impatience and his tendency to throw choleric tantrums. Casstorff knows about his weaknesses and works out in the martial art of Aikido to find his balance. His special strength in this sport is that he is able to think like his opponents. At work, he has found ideal partners in Eduard Holicek, a veteran superintendent, and Jenny Graf, his young colleague with fresh ideas and approaches.