Gereon Rath (Volker Bruch), after his return from Russia, learns of the death of his assistant Jänicke. Councilor Benda (Matthias Brandt) clears Rath on Jänicke's secret mission and instructs him to find his notebook. Rath is suspicious of one of his colleagues and makes a frightening discovery. When trying to help Rath, Charlotte Ritter (Liv Lisa Fries) is in great danger.