Night watchman Mahler adored his beautiful neighbor Melitta and secretly took photos of her private life with a telephoto lens. One day he captured a shocking scene: the girl's death and the face of the murderer. Police investigators have set out on a false trail, leaving Mahler as the only one who knows the truth. He decided to remain silent and use the film for blackmail. He had no idea how naively he underestimated his opponent.
