In the summer of 2020, there are still six people missing from Winden. The police have few, if any, leads and an external special task force is sent in for additional support. Clausen is the man in charge. He is an unconventional character who rattles off quotes from Freud. He doesn't have a driving license, so Wöller and Charlotte Doppler take him around as he questions various people in town. He quickly realizes that the residents in Winden have a lot to hide.
Season 2 : episode 7
The missing brother
When he visits the power plant again, Clausen brings information from the Marburg registry office with him. The investigator determines that Aleksander is several centimeters taller than the height listed in records from the 1980s. Clausen arrests him under suspicion of identity fraud.
During further questioning at the police station, Clausen reveals his true motive: His surname also used to be Köhler and his brother Aleksander has been missing since 1986. Clausen received an anonymous letter a few months ago promising he'd find answers to the case of his missing brother in Winden.
Season 2 : episode 8
Clausen wants to prove Aleksander has committed a crime and is quickly granted a search warrant for the power plant site. He goes straight to the cooling basin where the yellow barrels have been encased and demands they drill into the concrete.
Despite Charlotte Doppler's warnings, Clausen opens one of the barrels. An amorphous dark matter rises up from the barrel and within minutes, the apocalypse irrupts in Winden.