This one is closer to the straight drama of the British Edgar Wallace series, despite the presence of the ubiquitous Eddi Aren't, whose presence serves to lighten the tone; on this occasion he's the assistant to the investigating police officer, and displays an unexpected talent for wrestling.
It features so many characters and subplots - swindlers and forgers, gold-diggers and blackmailers; to name just four - that it's quite easy to get lost in the plot, or sub-plots, but as long as you concentrate on the main plot thread that treasure is buried in the grounds of Lord Chelford's estate; that it is being protected by a mysterious 'Black Abbott' figure; and that literally everybody wants to get their hands on it, you can settle back and let the proceedings unfold. It helps,also, that the investigating officer seems to have an uncanny knack of getting to the heart of the matter - without seemingly doing much investigating - and thus does all the figuring out for you.
Aren't aside, it boasts wonderful ensemble playing from actors, many of whom I've come to know and love as staples of the series, including Joachim Fuchsberger, as Dick Alford; Werner Peters, as Fabian Gilder, and a young Klaus Kinski, as an ex-con butler.
The film has a number of good nocturnal chase scenes, excitingly filmed. It also boasts a wonderfully kitschy soundtrack.
Ratings-wise, I'd probably say 7/10: the first-third of the film where too many characters are introduced causes it to drag, unduly; the final third more than makes up for it in my book; as does the ensemble playing, the chase and fight scenes; the music, and the nocturnal cinematography.