The body of Henry Budde is recovered from Lake Constance. Elena Barin and Achim Schatz begin a race against time when they discover that Stefan, the murdered man's son, has also disappeared. At the same time, independently of the murder investigation, Moritz Muhl, who has been injured in the head, is found in a hotel. He has no recollection of the events of the past few days. While the detectives are puzzling over whether Muhl is the perpetrator or the victim, they receive an anonymous tip: another victim is said to have been buried alive in a box in a forest. It's Stefan - and they have less than 24 hours to save him. When Elena and Achim come across a 30-year-old corpse, the confusion is complete. What role does Moritz Muhl, who suffers from amnesia, really play in Budde's murder and Stefan's kidnapping?