The gas station attendant at a Mainz gas station was shot. This is the second assault in two weeks, but this time it's fatal. The only witness is the blind law student Rosa Münch, who still lives with her parents and longs for a life beyond the overprotective control of her father. Chief Inspector Ellen Berlinger and her partner Martin Rascher investigate the traces of the two perpetrators and follow the indications of the blind: The smell of an expensive perfume, the voices of suspects, the details heard and felt by Rosa at the crime scene. The commissioners want to put the vulnerable witness under police protection, but the young woman refuses. On the contrary, when another unknown young woman, whose voice sounds familiar, tries to contact Rosa, she keeps it to herself. The experienced investigators suspect that Rosa knows more than she says, and have to continue investigating without their support and resort to unusual methods to prevent further deaths.