When DCI Barbara Kramer and her colleague Thomas Riedle get the message that a young woman from Buchingen has not returned home from a run, the local force and concerned villagers have already been searching for her for 17 hours. They face an uphill struggle to prevent evidence from being destroyed, a contingency which becomes more salient when a body is discovered 72 hours later.

Despite the team working many hours of overtime on the Berghoff case, there are still few leads to follow. The forensic team is able to isolate the DNA of an unknown male, but the databases do not provide a match. The discovery of a second body less than 20 miles away leads the team to believe a serial killer is at work.

A hair found in the Schora case leads the team to a suspect, but there is still no breakthrough in the Berghoff case. Navit's relentless data searches yield a surprising result – the suspect is implicated in the unsolved murder of a French student, across the border in Austria, four years previously.

Progress is slow as the investigation reaches the 100-day mark. As Kramer prepares to downsize the team, they finally manage to glean evidence from the murder weapon in Steinach, narrowing the search to potential perpetrators.