Krüger retired from active service and the Spreewald after Marlene's death. One morning he finds the body of environmental activist Chris Wenzel on a lock. Fichte and the young criminal officer Luise Bohn, who returned home after her training, start the investigation. The dead man had made some enemies in the region as a water worker and opponent of the Cottbus Baltic Sea. Krüger lives in seclusion in his construction vehicle in the Spreewald and mourns for Marlene, who appears to him again and again in visions. With the help of legendary figures from the Spreewald, she sends him signs that he cannot interpret at first. Spruce, Luise and Krüger come in different tracks to the property of Jasmin and Gerald Heyse, which is located deep in the Spreewald.
The couple tried to cope with the tragic accident death of their six-year-old daughter Marie, who completely destroyed the life of the young family three years ago. Spruce remembers: A little girl drowned when she was hiding in a fish box while playing and it became a deadly trap. The commissioners suspect that Chris Wenzel may have died in this place. The „ Spreewaldkrimi – Dead Don't Mourn " is a multifaceted story about the loss. The typical nested „ Spreewaldkrimi " dramaturgy follows the theme of the farewell to the previous film.