Ghosts or other supernatural phenomena do not occur this time. But the ordinary crime has indeed its appeal. Puzzling is the result anyway: How could the black cat thief escape over a vertical fence? What's so valuable about the cat? Why is the circus sabotaged? Questions, questions, to which there is convincing answers at the end. And for voltage is also provided: A lion breaks out, the question mark a break and at the end there is a showdown that leaves nothing to be desired in drama left.
Positive also falls to the role of Andy, a boy "from the construction" (= circus), who eagerly participates in the investigation. Often the question mark to get a yes something amateurish acting as spokesman peers companion aside, but Andy aka Stefan swath does his job very neatly. Another plus in my view is the fairground atmosphere, which is mediated quite convincingly by an atmospheric soundscape. My favorite quote comes from this episode thief: "Now ye are wise guys Let's see that ye be not too smart times.." Also the output of Justus motto (see headline) will be remembered.
One problem with early radio plays is that their duration is very short and had to be deleted dramatically in the books. So at some point are a strong man and a clown on the list of suspects, without knowing how they are then advised. There are only the comment of Bob: "We are just Detectives and know something." And as the question mark Hauptkommissar Reynolds report the license plate of the thief, a cop calls already a minute later on, to indicate that the car was found.