The SOKO Köln investigates the cathedral city with humor and often with hard work. Their cases take them into a variety of environments, from the Cologne clique to the terraced housing estates on the outskirts of the city.

Two sisters who couldn't be more different are unaware of their father's double life with two families and the existence of the other until his sudden death. While stuffy Sandra has no need for such a relationship, chaotic Sandy never leaves her new-found sister's side.