During an International Medical Congress in Salzburg, a well-known surgeon and scientist, Doctor Thomas Steinmetz, is mysteriously killed. When Inspector Quentin Neuner examines the corpse, he notices something he has never seen before. The victim's right foot had been dressed in a colourful hand-knitted sock, and his shoe nicely draped next to the body. Was this a sign? Or the signature of the killer? If so, what is the killer trying to flag up? In the course of the first interrogations, the killer strikes again in broad daylight and right under Quentin Neuner's nose. The investigators quickly discover similarities between the two victims. Was it their research that sealed their fate?