Münster. Private detective Wilsberg is given the task of solving a suspected murder. Since the case happened 16 years ago and was filed away by the police as a suicide, he initially approaches the investigation with little motivation.

Private detective Georg Wilsberg is looking for farmer Rabenalt's runaway adopted daughter Tanja. Immediately after he has brought the girl back, he receives a follow-up assignment from Rabenalt's son Karl-Hermann: Wilsberg is to track down a woman who is secretly involved with his father. Without knowing it, Wilsberg knows the woman he is looking for, because it is Ines, an old school friend who has just met him in Münster. He therefore suspects that this meeting was not a coincidence, but a calculated move. That same evening he receives a call from the desperate Tanja: her adoptive father has broken his neck in a fall down the stairs; her brother has been arrested on suspicion of having pushed him. Tanja herself is in hiding so that the youth welfare office cannot take her away. Wilsberg finds her in a barn and takes her to his antique shop...