The series Harbour Detective is a spin-off of the well-known and successful TV detective series The Roth Detective Agency. However, in the series The Roth Detective Agency, the detective was named Albert Loffelhardt (portrayed by Klaus Lowitsch). In The Roth Detective Agency, Loffelhardt disappears from the screen abruptly, and the agency is taken over by Egon Fetzer. No one knows what happened to Loffelhardt.

Loffelhardt reappears in the series Harbour Detective. However, he is now calling himself Benno Stepanek. In the first episode, „My name is Stepanek“, Stepanek is recognized by Commissioner Poltisch, who also made several appearances in The Roth Detective Agency, after conducting an investigation.

He then approaches him: „Would you look at this... Loffelhardt. I thought you would be in India or Malaysia or something of the sorts.“ The only answer that he receives is: „My name is Stepanek“, to wich Commissioner Poltisch merely replies: „Oh, no.“ He takes a closer look at his badge, which contains the name Benno Stepanek, and says: „If I didn’t know that you were Loffelhardt…“ Loffelhardt alias Stepanek then explains to the commissioner that his official name had been Benno Stepanek since July 14th of the same year.

It is later revealed that Stepanek has taken on the name of his father, who died in Africa during the 2nd World War and who’s grave Stepanek was looking for during the holidays, when he was away from Duisburg.

Stepanek has now returned to his home country and is working yet again as a detective in Duisburg. He is particularly engaged as a private investigator in Europe’s largest inland harbour, that of Duisburg, and stumbles again and again over the authority of state, inforced by the Head of the Criminal Court, Toffer (portrayed by Hellmut Lange), who often requests his help in investigations that require undercover work and an unconventional way of exposing new information.

Further characters that are already familiar to the public from The Roth Detective Agency also revolve around Stepanek. Among these we would like to mention barkeeper Franz and his helper Irene, to whom Stepanek was previously known as Loffelhardt.