Frank Koops is a police officer in the small mountain town of St. Andreasberg in the Harz Mountains, which is usually quite tranquil. He is known in his area with his green Lada Niva and everything seems to be going well. But crime also penetrates into these hidden corners. Koops masters challenges in his very own, calm way and his criminalistic qualities are always underestimated by the criminals. His specific local knowledge is also an advantage. He is friends with the postman Heiner Kelzenberg and his young colleague Mette Vogt from the neighboring town of Braunlage. Both are important helpers in an emergency.